Crazy-ass Devil May Cry bosses

Agni and Rudra
The PJ and Duncan of Devil May Cry 3 - two muscular demons who keep their heads on their sword hilts. Kill one of them, and the remaining one combines both of their blades into one super-chopper. Kill both, and they beg to come with you. Dante, never gracious in victory, agrees on the condition that they shut up. Reasonable enough.