Top 10 Most Difficult Bosses in Mortal Kombat
Every Mortal Kombat game has a boss, and no matter the difficulty level, they'll always be tough to overcome. But how many attempts did that take before frustration set in?
Shao Kahn could easily have been #1. He is difficult in every single game, as he should be. In the second game, he literally taunts you, making you feel like a weak kombatant compared to his superiority, when in reality, you have a chance.
In the next game, you have to be focused to beat Kahn the second time around. The third game of the franchise is the hardest Mortal Kombat game to date based on the overall aspect. Some say MK 9 Kahn can be beaten, but to tell you the truth, he is once again not a cakewalk for anyone.
Definitely shows how impossible it was to beat this boss. The most difficult boss in Mortal Kombat history.

This four-legged Centaur is ungodly compared to everyone else. He blows them all away just by his one appearance as a boss character. Seriously, how can you dodge his projectile that takes half your life? You would be caught off guard right from the start.
Even worse, as one pointed out, he can indeed teleport side to side. How can we make this brutally hard character even tougher? Yes, even tougher than Shao Kahn, just in this game alone.
This guy was extremely cheap. His moves do a lot of damage, he could teleport, plus all projectiles are useless.

Goro definitely symbolizes the iconic boss that he was in the first game. Most people remember how ungodly he was, just picking up the opponent's torso and taking a ton of damage. He was the first true boss with the purpose of owning you in Kombat after many tries.
He hadn't returned until Mortal Kombat 4, where he was still fairly tough but could take a ton of damage. In MK 9, he was slimmed down like Kintaro, where you had a chance to beat him, as well as in MKX, which I don't consider him a boss in that game due to the fact he is pretty much mortal at that point.

Mortal Kombat 4 Shinnok was more about defeating him for the purpose of the story and less for the boss battle. MKX Shinnok on the hardest difficulty is, to me, impossible to beat and harder than Shao Kahn on very hard. Shao Kahn may take a long time to beat, but Shinnok on the hardest difficulty in MKX is harder than Kahn and even Onaga, whom I found harder than Kahn as well.
It's easy to damage Shinnok, but actually defeating him is hard to impossible on very hard due to his spamming that amulet. With Onaga, you break the Kamidogu to weaken him. I haven't had a boss battle this hard since Onaga, but Shinnok's amulet spam makes it impossible to win.
Kronika is tough too. I find Shinnok the hardest, then Onaga, and Kahn is actually the easiest out of the main bosses. Kronika is as difficult as Shinnok, maybe a bit easier as she doesn't spam. Shinnok is the hardest and most fun due to his story. He is more powerful than Onaga, who is more powerful than Shao Kahn. Only a boss more powerful than Shinnok now is Kronika. That alone shows how powerful one must be to topple an elder god, aside from the Cage family defeating him.

Deception is my favorite of the 6th generation games Mortal Kombat had out there, and this guy I both like and hate at the same time. I can't tell you how many times I kept trying time after time just to beat him. I literally had to cheat by having lesser time to beat him. That's how difficult Onaga is.
Half the time, he's durable because Shujinko gave him the Kamidogu, as explained in the intro and konquest mode. You must knock over all six of them without taking too much damage. If you can do that without losing patience, well done.

Kintaro was absolutely brutal in Mortal Kombat II. However, in MK 9, his difficulty level slimmed down dramatically to the point he could be beatable, similar to our next kombatant.

The game in general I felt shouldn't have been made. It might as well have been Marvel vs. DC, but I digress since the fatalities were god-awful. It all comes to play as you find out both villains merged into one super boss being. He is kind of tough enough to surprise you for such a game that feels strange if it counts in the realm of Mortal Kombat.

Yep, the technical first boss of the game was actually not as difficult as the semi-boss of the same game. Luckily, he had another game to be another boss in Deadly Alliance, but like in the first game, he didn't feel anything like a boss compared to others.
In the later games, he pretty much is just as mortal as the rest of the kombatants.
He was more cheap than difficult. For starters, he has the fireball projectiles that shoot several of them in your direction, making it difficult to get near him. Plus, he has the ability to transform into any combatant, including Goro, forcing you to change your strategy on the fly.

While he has a lot of similarities to Onaga's moves, the difference is his actual mobility when he is in his giant form. While he might seem to be the most undeserving of his massive push to being a boss, you can't deny that awesome intro to the game.
He is tough enough, but he is definitely beatable at least compared to these other five remaining bosses who all have memorable fights.

Ah yes, Kronika, the time-shifting boss. The first female boss as well. She takes a fair amount of combos to beat in one round. If you want to be cheap, just attack fiercely in the corner.
I found Kronika harder to beat than Shinnok in MKX. She was an unfair fight in my opinion and ten times harder than any other fight in 11's main story. However, she was a fantastic final boss for the game.
The best way to beat her is to hit her over and over in the corner.

This oni demon takes a ton of punishment as a semi-boss. You literally must do combo attacks. Otherwise, he is tough to get through.
The best way to beat him is by using your weapon. The best characters to do this with are Kano and Hsu Hao, who have the same basic weapon. Continue to use the combo where you attack in a circular movement, blocking when needed. It may sound cheap, but so is Moloch himself.