Last "boss" level of Catherine, even on easy mode, was a complete fucking nightmare.
Last boss on the shite that was BulletWitch went unbeaten for me. I spent 45 minutes blasting the shit out of it, and did fuck all. Traded it in the next day.
I remember a game on a friend's C64 called Barbarian... dead easy to beat all the opponents in the 1-2-1 fights (think Conan in a Mortal Kombat/International Karate style original setting) yet every time it came to the big wizard boss everyone I ever saw play it got burned to a crisp! That beardy old cunt was nigh on invincible!
I am hungry, I am incorrigible, I AM BEAR!
I did not beat him. Stupid boss.
Do or do not - frankly my dear, I don't give a damn.
I can't remember a boss that I couldn't beat in the end, but right now I'm trying to defeat Cthulhu in the "The Stars Are Left" DLC for Magicka. Damn, that squid is a real bastard and we had a few tries now. But we're getting better and I know for sure that it'll feel GREAT when I see him collapse into a big pile of shrimps.