Gamers expect the final boss to be arduous. After playing a game for weeks or months and enduring every puzzle and enemy thrown at you, it would be disappointing if the big bad was anything but.
The last adversary should serve as a test to see if the player can apply all the skills they hopefully mastered throughout their playthrough. But the progression of difficulty isn't always gradual or fair.
You could be only halfway through your adventure, still getting used to the controls, when you encounter a sub-boss that redefines the term "difficulty spike". Sometimes, they are harder than the final boss. What's worse is that none of the enemies on this list are optional. It's mandatory to face them.
If you can't beat them, you can't complete the game.
Whether it's because of their instant-kill attacks, their cheap tactics, or their unblockable moves, these villains are deservingly known as the most unreasonably difficult sub-bosses in video games.
Bosses are supposed to make you feel satisfied once you defeated them. But once you beat this bunch, you were just relieved it was all over.
10. Kintaro - Mortal Kombat II
If you thought Goro was difficult in the original Mortal Kombat, wait until you face the penultimate of the sequel. Before going head-to-head with Shao Kahn, you must face his champion; the four-armed Shokan warrior, Kintaro.
This tiger-skinned monstrosity only takes half-damage, has an immunity to certain attacks, and is strong enough to kill you in four moves. He almost never stops moving, so you're always on your toes.
The most vexing thing about Kintaro is his tendency to leap offscreen and then drop down on top of you. Not only does this teleport stomp make mincemeat of your health bar, it's the only attack in the game that's unblockable.
If you're playing the Super Nintendo version of MKII, you only get a measly five credits. Even if you don't lose a single life before facing Kintaro, you only have five tries to beat him or you have to go back to the start.
The only saving grace is Kintaro regularly taunts you throughout the battle, which is the perfect opportunity to attack him. If he didn't take time to gloat, he would be borderline impossible to defeat.