Top 10 Hardest Bosses in Dark Souls II

The first phase is a nightmare with DS2's stiffer controls and the adp stat. This guy is almost too aggressive for that game's speed. The second phase is slightly easier but not by much. It's easier to dodge his attacks since he only uses one sword, but dear god the damage this guy does in this phase. He'll pretty much two-shot you if you aren't careful. If he already isn't hard enough, there are statues around his arena that will heal him if he gets close so you have to have enough wedges to stop them or this fight becomes a frustrating disaster. Oh and if you summon phantoms to help...good luck, that only makes the fight harder since he'll annihilate them in a couple of hits and leave you soloing a boss with double, triple, or quadruple his already tanky base health.
This boss gave me so much trouble when O first fought him. Honestly, he's not that bad once you get the pattern down, but he's still a challenge. The second phase is the easier one with the only bad parts being that flamethrower attack and the AoE blast. Both aren't bad to avoid, but the rolls have to be on point for them. The FIRST PHASE is a whole different story! The combos are long and hard-hitting, and he gives you no time to heal. It's like Gwyn except you can't riposte him. And to make things worse, he has a fairly tanky health bar that can be healed if you don't put wedges on the sides before the fight starts. This boss took me over 40 tries so I can't NOT say he's the hardest.
Imagine playing Ninja Gaiden where you can only take 3 hits and the floor you step on will burn you if you stand on it for too long. That's this boss. There's little time to heal, he can pummel you quickly even if you're a tank, he's very fast, hard to predict and dodge, and he has a lot of health. Learn to dodge, be patient, don't run out of healing items, and you MUST solo this boss. Bringing a friend will only make his resistances more ridiculous. Good luck, and may the Sun bless you.
It is worth noting that you can force the Fume Knight into phase 2 at the beginning of the fight if you wear Velstadt's helm. Some people find it easier to deal with him this way, as his attacks are more predictable when he only has one sword. But no matter which way you decide to do it, this guy will undoubtedly kill you many times before you succeed. Good luck.

The boss fight, itself, is pretty difficult owing to the hit radius and power of their attacks. Plus there's two of them.
However, the true cruelty is the abandonment of Dark Souls' "hard but fair" mantra. You have to traverse a difficult and expansive stretch of frozen wastes every time you attempt this boss fight. Hard hitting enemies with lightning attacks will continually spawn and force you to burn precious healing. There's no bonfire adjacent to the boss's room which means every failed attempt results in a lengthy and difficult journey just to get another crack at them.
The whole affair feels unfair and unnecessarily frustrating. It is the first point in the game where I said to myself, "This is no longer fun."
Welcome to the frigid outskirts, or as Tylerlangford1224 said, the seventh circle of hell.
This is the biggest place in the entire game.
There are no bonfires in this area.
There are frequent snowstorms that makes it hard to see where you are going.
During snowstorms, at least one electric ice horse will charge towards you, and because you can't see very well during snowstorms, they will likely deal damage to you before can see them. The exception to this is when you are close to a house, in which case they won't spawn.
Finally, the fight itself.
It's like fighting against Aava again (which already was a tough boss to begin with), but this time in a much more smaller area, and two of them at the same time.
By very far, the hardest boss of the game. Completing the convoluted path filled with those annoying Lightning Horses was a hard task, let alone taking the boss itself! Having no bonfire next to the gate fog was cruel. I mean, Aava was already hard, imagine fighting two of them at the same time; took me so many attempts!
One of two bosses I fought with summons other than the belfry gargoyles. I decided this boss was made unfun and wasn't worth the effort after running through that absolutely terrible area that I'd rather not talk about. The boss itself is difficult and could have potential if it had a normal path leading to it.

How are they this high on the list? Sure, they're brutal for a new player, but they're a joke for veterans.
The difficulty of this boss is due to facing him in the very beggining of the game. Being gank spanked by those two (or three if you messed up the fight) agile Sentinels was excruciating. The windows for attacking were so rare
I blew these poor bastards out of the water with nothing but a tower shield. They are a nightmare for noobs and a nothing boss for veterans
I remember struggling a lot for the first time but eventually I got in on my 4th try. Afterwards (NG+ etc.), the sentinels are low-level enemies at best. This shouldn't be this high on the list.

One-hit kills... I remember that my Dragon Shrine stage was already with no enemies given the times I completed it after several deaths at the boss fight. The boss isn't that hard but the one-hit kills and the very large HP transformed it in a test of patience where one mistake was fatal. And escaping from that diving fire breath was very hard and tricky
Just tedious an boring. Run in, take a few hits and RUN away, then RUN back and repeat. If you do it wrong he one-shots you. Fun.

Real name of the boss: Afflicted Graverobber, Ancient Soldier Varg, Cerah the Old Explorer. Guess the site found it too big and edited
Kind of and understimated fight. As a melee build it is very hard indeed. You have to be so aware of the enviromnent and there is no place to rest; such a tense fight. And the journey to the arena in painful also.
Tied with royal rat authority for worst boss in the series.

All of the other bosses solo took under 10 tries with a few under 20. While I was tired and wanted to beat this boss and go to sleep, I found it extremely difficult and it took me probably 70 or 80 tries. I may have been under leveled I'm not sure however he consistently killed me in 2 hits or 3 if I was lucky. I found some certain attacks very difficult to dodge and couldn't find good windows to heal outside of the AoE attack. The run up to this boss is also only second to Lud and Zallen which isn't hard to beat but it's pretty horrible. Overall it was a difficult boss but a well balanced one.
I wasted 15 effigies, 25 twinkling titanite upgrades and 50000 souls just to beat although that jeopardized completing the rest for dlc.
The reason for that is because I died more than 60 times either by him or by trying to reach him which is probably more difficult!. On one occasion we killed each other at the same time but it counted for him because I died 0.1 second earlier!.
To succeed you either have to be expert in dodging which I don't recommend anyway because one mistake is probably fatal or maximum upgrade Havel's shield infused with magic and also magic resist armor.
You should know very well when to attack and when to heal as he hits like a truck once you're healing he will attack you immediately.
I only beat him because the game somehow glitches so that he didn't buff himself to constantly radiate magic damage. Before this happened, though, he killed me a pretty good amount of times.
I died 80 times (give or take). Fume Knight is a nightmare too. Both are the hardest bosses I've ever fight with since PacMan. Each of them is even harder than the infamous Ornstein&Smough. (I beat Demon's Souls & Dark Souls).

The Hardest boss in the Vanilla game so far. It is almost impossible to beat him if you're a melee character, somehow you're forced to use lightning spells or fireballs to kill him when he uses mitosis before he kills you, has a huge variety of spells, and some of them are very hard to avoid (like the dark bomb), specially when he ganks you doing the same attack divided.
Every other boss, I can pretty reliably take down in no more than 3 tries, or they have decent npc summon options. Not this guy. I've only beaten him twice, and both times it was by cheesing him down with pyromancy. I must have burned through close to 20 effigies before landing the perfect firestorm.
Another hard fight and the necessity of giving away a Human Effigy each time was kind annoying. When he clones himself, you know it got real so keep one eye at his HP and buffer your weapon with lightning to go berserk at the right time. Don't let the fight with the two be long enough to get yourself killed
This angle of death delivers and is one of the few bosses that are actually a challenge, the fact that you NEED effigies to fight it puts on pressure on you every time you die the. Oh and that splitting in two thing...no.

The boss isn't that hard. What IS hard is the rats at the beginning. If you get toxic, it's all over from there. The best thing to do is lure them and use Lingering Flame.
This and the Smelter Demon are the only ones I'm yet to beat on the vanilla game first section (getting the 4 great souls).
My brother brought his friend over for the weekend once, and they played against this boss, it was very entertaining.
Not the hardest fight of the world, but his headbutt is nearly impossible to dodge and the shield is useless. The beginning with the smaller rats is kind tricky too.

Another awesome fight! Isn't that hard because you can block all of his attack with the Royal Kite Shield, the most basic shield of the game; if wasn't for that, this would be one hell of a hard fight. Again, another hard path culminating with a boss fight without a Bonfire along the way
This guy should be right under F. Knight. He is astronomically difficult! I had no luck blocking at all, had to dodge and 2-hand my weapon. Does HUGE damage with that dai-katana, and has considerable health. I think Fume Knight is hard for strenght, and this one for dexterity.
Took me hours, till I realized you need to be light and not greedy with hits. +10 rapier did the trick for me.
Changed my mind about fume knight being the hardest. This guy is. This is because of how fast he is.

OH MY GOD this boss does not belong on this list. the very first time I fought this boss I was intimidated by its sheer numbers but once I started spamming spells this boss was down in a matter of minutes. all you have to do to win is run around the map train them into one spot them start spamming spells. dark orb and heavy great soul arrow are good choices. once they start going on the defensive just dash to the other side of the map. they don't have any way to defend themselves so they go down pretty quickly. and if your a melee fighter sure its harder but all you have to do is bait their attacks then swoop in and punish.
This boss is a paint in the a**... like seriously, either you rush it, or you have to kill like 3 or 4 at the same time. Especially if they stay compact together, it gets really frustrating... This is the only boss I never killed in the entire Souls series...
The boys! I fought these guys after Belfry Sol, so I didn't expect guards other than gray phantoms. But these guys knocked me flat. Turns out Disney's Hunchback severely underestimated the power of gargoyles.
The reminder of the frustation in Bell Gargoyles boss fight at the previous installment comes immediately as soon as you enter the arena. Thought facing two gargoyles was hard? Imagine five!

This fight is absolutely epic. The knights getting ready, the entrance, the fight before the king shows up, the boss fight, everything. I loved this fight.
One of the best boss battles of all time. Very tricky but fair to be honest. Very doable as long as you pay close attention
Definitely one of the best fights in this game. He's fast, difficult to dodge, has high DPS, and has above average health.
A difficult well designed boss but not too hard.

That damn camera

Hardest fight for me. Took hours. Tried with every combination of gear I had. Tried with summons, and without. Finally got her down as hollow, lots of health missing, no summons, and no shield. I'm the boss now
This THING summons Velstadt. While shooting overpowered magic at you and teleporting wherever it wants. Even so I still enjoy the fight, but it is really difficult.
Been breezing through scholar till now. I've completed vanilla but not any dlc. This is the toughest boss I've fought so far. That health though!
Most of the time she summons Velstadt instantly - if you kill Velstadt, she just summons him again, if you focus her Velstadt will all of the sudden lock onto you, and 2 hits by her and you are dead. Also the NPC summons don't deal any dmg to her.

Not the hardest, but one of the best fights, with the ambiance of the arena and the looming, brooding, silver knight who claps lightning while you're wet. I had a really huge Greatsword (Ultra Greatsword) and when it hits the shield's hit box, it bounces right off. Fun fight. Definitely worth the duel.
One of the best bosses in the game.
Best boss fight in the game.

Without using the ballast, this boss takes 20+ tries on the first go. What a headache for newer players.. once you're a veteran, it's a bit easy as long as you roll and poke him with your sword
His moves are incredibly predictable and easy to dodge.
You must exclude the (cheap) ballista, and rate the boss itself.

This is a hard hitting boss with a good bit of health. It was one of my more difficult fights in the game but it never felt too unfair other than some big hit boxes.
Very fast enemy that's tricky to beat. Nowhere near as hard as the battle where you face two of them, but still rough

What I intended to do was use my bastard sword +8 on the path to him, and then switch to my Raw Bastard Sword +10 for the actual fight. I forgot to switch. That would have made it easier. My armor was Vengarl's armor and gloves, and the hood and leggings from Straid. I also had Idol's chime and 44 lightning spear.
This guy. If you're going solo, you're screwed, not to mention Agdayne being barely any help. It's best to bring Scarlett if you can, as she's tough and will actually heal herself. Velstadt is a giant tank that hits like a truck, but his attacks are predictable (although the AoE makes it hard to dodge).
Not a bad fight at all. Decent size windows to heal, attacks blockable with a shield. The only thing to worry about is phase two with his magic attacks. But as long as you stay close to him they're nothing to worry about.
Meh. He should've been a fight for earlier in the game. Every giant fight has prepared you for this guy's telegraphed attacks, but he hits really hard.

It depends, really. If you don't have giant souls or don't have 5 of them, good luck. His defense multiplies by 72 without giant souls, whereas it's pretty weak if you do have 5. An Old Whip and Soul Appease will put him down quickly, but be careful, as his attacks are devastating (although predictable).

This is one huge adrenaline rush. Having to manage two well-rounded characters that are scaled for endgame means you're in for quite a fight. Be sure to kill them quickly, or one will revive the other.
The challenge here is to beat them solo! I wasted 4 effigies, 25 gold pine resin ( approximately 40000 souls ) to do that. Their ability to revive each other after one of them is killed is a real pain in the ass.

This fight is easy if you know what to do. bring alluring skulls to group the skeletons, kill the necromancers and hide in the doorways when the boss rides by. after skeletons are dead use lingering flame with the hexers hood for the bonus. after his health is down enough he wont be able to make the jump, hit the horse once and victory is achieved
This boss is cool because of the corellation between him and the area where we meet him!

He's easy for ranged characters, and somewhat difficult for melee. In fact, get him outta here.

Having to hit the heads only was the trickiest part... And the spiders that attack you...
Nothing too terrible, but can be incredibly agonizing to get to.

To sum this bugger up: high resistance to everything, high health, fire damages nearby players, giving the middle finger to melee users, highly-damaging spells, and worst of all, absolutely nothing meaningful as a reward for beating him.
Screw this boss fight.
This fight is a pain in the a**! Every time I think I have her, then she jumps out of the way.
How is Covetous demon above this? That doesn't make any sense.