Imagine the Operation board game set in a labyrinth, and multiply the difficulty by 10. That would be just the first level. I can't think of any game as consistently demanding and intense in regards to accuracy and speed. Just brushing against another object or wall is an instant loss, and some later moments are the only instances I would call the requirements in a game "pixel perfect". Although it's only six levels, the last three would hold the 1st, 2nd, and 3rd spots on this list if they were individual games.

Requires an incredible sense of physics, timing, depth, and strategy once you get past the first dozen levels. Even in the second half of normal difficulty, there’s very few instances in which you'll survive from a single error in tilting your board. The sequel also ramps the challenge with a significantly heavier focus on stage gimmicks when compared to the original.

You might get three hits per stage, but you'll need them. Once you reach the last 1/3rd of the game, every boss battle is pure chaos.

sans.

Smooth controls and a huge range for your gun keep this from being impossible. The respawn system is also fairly forgiving. Everything else demands your constant attention.

Controls are very rigid, and nearly everything is significantly more mobile than you are. With only two hits per life, you have to know exactly how you're navigating the enemies and pits.

The game consistently reminds you that "No Attack is Unavoidable", but you still have to be fully focused on every obstacle to make it true.

When playing as Maria, this is probably the easiest game in the series. When playing as Richter, it's the hardest Castlevania I've ever played. The backflip and slightly more control while jumping are barely a match for the faster and more numerous enemies.

One of the most deceptively difficult games ever, combining a simple concept with stages that leave no room for error.

One of the most famously limiting games in terms of controls and attacks, but there’s just enough freedom to always succeed.

Very faithful to the "NINTENDO HARD" gameplay style that the AVGN loves to feature in his series. There's a lot of trial-and-error, but at least the game offers numerous checkpoints and infinite lives (on most difficulties).

With the sheer amount of variety in gameplay, it’s amazing how consistently challenging the levels can get with their individual theming. It’s a fair difficulty curve, but it reaches very high.

An iconically bizarre shmup and a surprisingly hard one too. Screens can fill up with projectiles in the blink of an eye if you're not shooting enemies right as they get onscreen, and taking one hit sends you back to a level checkpoint. Of course, dying also takes away power-ups, making the game only harder and harder with each death.

Definitely the most times I’ve hit the “reset” button on a game. A single inconvenient blast or stomp can destroy most of your squad and an entire day / dungeon run within the game.

A certified "bullet-hell" shmup. With how large your ship sprite is, practice is mandatory. Luckily, the difficulty is softened with some instant respawns and temporary invincibility from sub-weapons.