Originally Posted by buta
Does it unlock stuff before the fight, though? I wanna get to A3/4 to farm but I'm too lazy to restart when I bump into impossible elite mobs. >_>
As far as I know, nope.
I stumbled upon this on accident. I meant to fight Diablo on Normal mode for the "Punch Diablo" achievement really quick and ended up punching Inferno-mode Diablo. The rest of my group was like "wtf?" and they left me.