Scary bosses?

[Scratch_Porkings]

I never got scared at a silly little video game boss, all devil eyes and horns or you've got to shoot a helicopter a hundred times... But those shiny happy mahoosive bosses in rainbow islands put me out of my comfort zone.

[RuySan]

That bastard vampire at the end of Rainbow Island world 3. He's my arch nemesis.

Also, Dark Souls is filled with scary bosses. I can't choose just one of them.