Top 10 Most Difficult Nintendo Bosses

Inner Agent 3 - Splatoon 2: Octo Expansion

I'm feeling nice, so I'm going to tell you how to beat this boss.
First phase is the Inkjet phase. Deal as much damage while she's on the ground. Then, when she's in Inkjet, do not stand still or she'll break your armor. Jump and move a bit until she moves into the next phase.
With the bubbles, it's really simple. Get behind her and shoot. Do not get in front of or behind the bubbles. She'll throw a bomb, causing it to explode. Just deal enough damage.
The Autobomb phase can actually be the easiest if you know how to do it. First, ink as much as you can. She is always aiming at you and cannot ink the floor, causing her to be unable to shoot. This is your time to deal damage.
The next phase is easy. Chuck two bombs onto the UFO. Done.
The next phase is the last and the hardest.
DO NOT STAND STILL.
KEEP MOVING.
Go around the walls and deal damage while she's trapped in the ink.
If done correctly, you should be done!
YOU'RE WELCOME, PEOPLE!
Byeee
You can thank me later!

The Hag 1 - Banjo-Tooie

Very difficult to pass on replay mode with 5 health! Dodging the back lasers and positioning to get the clockwork Kazooie eggs in on time is difficult but worth it.

Master Core - Super Smash Bros. for Nintendo 3DS and Wii U

Bonetail - Paper Mario: The Thousand-Year Door

Bonetail is not too difficult if you have the right equipment. The difficulty is apparent because you have to battle 99 sets of enemies in a row without dying. Most likely, you'll drain your resources if the enemies beat you up really well. Other than that, the actual boss is about as difficult as Bowser from Paper Mario 64.

Ganon - The Legend of Zelda: Ocarina of Time

It took me forever to figure out how to beat him. I hated having to go through the castle every time.

Bouldergeist - Super Mario Galaxy

Is this hard? People are crazy. The attacks are slow, a million bomb Boos spawn each time, and he's so big, you can't avoid hitting him.

Definitely the most difficult boss of all time. It is much harder than you'd think. Really impossible.

Hardest non-final, non-secret Nintendo boss.

Tabuu - Super Smash Bros. Brawl

Beyond incredibly hard on Intense mode! Should be number one!

Cackletta (Final Battle) - Mario & Luigi: Superstar Saga

Cackletta is a witch from the Beanbean Kingdom and the main antagonist of "Mario and Luigi: Superstar Saga." She is known for her maniacal laughter and plans to conquer the Mushroom Kingdom by stealing Princess Peach's voice. Her name is a pun on the word "cackle," emphasizing her witch-like persona... read more

One of the only times a Mario boss has been hard was when I was about to pick Bouldergeist but realized one of the only reasons I was terrible against him was that I was not good at 3D Mario games, and I still kind of am.

Spend a turn healing, dodge, and then you should be good. Doing this with no heals and 1 hp, however, is a valid reason to rank this as hard as it is.

Great call for a difficulty spike!

Weldar - Banjo-Tooie

The Shadow Queen - Paper Mario: The Thousand-Year Door

Tip: When Shadow Queen uses her hands, charge up Yoshi Kid with Mario's turn, and use the Stampede to wipe out the hands for two turns.

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Void - Kirby Star Allies

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Silver Fury Bowser - Super Mario 3D World + Bowser's Fury

Mike Tyson - Mike Tyson's Punch-Out!!

Mike Tyson should be number one. Most of these bosses are vastly easier compared to him.

I was only able to beat him by using the Nintendo Switch Online rewind button.

Instant kills with every hit for 90 seconds.

Shadoo - Super Paper Mario

Red - Pokémon HeartGold and SoulSilver

Red is a Pokémon Trainer from Pallet Town in the Kanto region. He is the first playable character in the Pokémon video game series, debuting in the original Generation I games.

He has since reappeared in various Pokémon media, including the Generation III remakes FireRed and LeafGreen, which are... read more

This guy is number 17? Try the Battle Tree in Ultra Sun and Moon on Super Battle, and beat him!

Mimi (Second Fight) - Super Paper Mario

Gyorg - The Legend of Zelda: Majora's Mask

Why isn't he on this list? He is extremely difficult! You need to get in the water to hit him and if you don't escape from the water quickly, you lose like three hearts!

Marx Soul - Kirby Super Star Ultra

Dark Link - Zelda II: The Adventure of Link

The only reliable way to beat this fight makes you feel like a cheater, but if you try to fight him any other way, it's basically just luck-based.

Grodus - Paper Mario: The Thousand-Year Door

Hooktail - Paper Mario: The Thousand-Year Door

Bald Bull (Title Defense) - Punch-Out!! for Wii

Bowser - Paper Mario

Fiery Gobblegut - Super Mario Galaxy 2

Mother Brain - Super Metroid

Mother Brain is a fictional character created by Nintendo as a primary antagonist in the Metroid video game series. First appearing in the original Metroid game released in 1986, Mother Brain is portrayed as a biomechanical supercomputer. The character plays a central role in the series' lore, particularly... read more

Queen Sectonia - Kirby: Triple Deluxe

Second hardest boss in the Kirby series. Quite unpredictable and has some inescapable attacks. And her soul form...
Star Dream is harder, though, but I didn't see him anywhere, so...