This can be from any console and any game.
I have heard alot about Pennence from FFX and how hard he is, but I can not get past Dark Yojimbo. I kind of cheated on the other dark aoens by summoning yojimbo and then zanmato them.
But what is a boss that has had you sweating, breaking your knuckles, gone into a fit of rage, had your heart beating as fast as possible because you nearly defeated them but you dont have much health? what is the hardest boss in a video game ever?