@windmill
I'm not really sure what to categorize him as, since he doesn't seem motivated by financial gain or passion. He's been indoctrinated from childhood to murder at command, for reasons he doesn't seem to question. "Serial killer" is the broadest category I know for someone who murders a lot for whatever reason. Technically he's also a mass murderer (or a spree killer), since we see him murder a bunch of people at once.
I think you're all too harsh on Peepman as well, he seems to be genuinely concerned for Misaki-chan. Sure he's a creep and a pervert, but let's not put him anywhere near the same level of amorality as the yakuza or Fable himself. Peepshots are not equivalent to murder.