Who else than the great Sans? Holy God the farthest I've gotten up to is the circular barrage of lasers which I fail to pass before he reveals his special attack, and that's with more than half health. I totally suck balls at bullet hell type things, so I often get hit by some of the simplest attacks early on which just makes me want to forfeit and start the fight over.

Those bones on the menu buttons are a load of shit too. While Undyne was pure bullshit all around, I've honestly had no real issue with Sans since he is almost entirely skill-based. But the menu bones are just unfair; needless depletion of health that you so desperately need, and it almost renders healing obsolete on top of the fact it pressures you to make your choice quickly or else you'll waste all your health.

On top of that, when he gets exhausted and starts throwing you through rapid series of random attacks, you often find yourself moving a bit after the previous one and it throws you off. It's really hard for me to process what's going on as it happens and because of the strenuous nature of them, I often find myself getting screwed over most by them, in perfect preparation for all the pre-special attack shenanigans.