Pitch is the Captain of The Nightmare Galleon, a twisted black ship drifting through space, run by a crew of Dream Pirates. Weidling a GIANT harpoon, Pitch chases after shooting stars and drags them to their doom. No further explination required.
Special mention to Sandy for not only facing off against Pitch and his crew, but narrowingly escaping and landing safely on Earth and becoming MIM's first guardians, single-handedly watching over all the children of the world and rounding up each of Pitch's remaining Nightmares.
Despite making chocolate, Bunnymund refuses to have any during book 2 when he first appears, because it has side effects. When he and North realize that the odds are against them and the children are in danger, he pulls out three chocolates. North snaps at him for offering at a bad time, and he calmly replies that he wasn't offering. And after three chocolates, Bunnymund goes from a calm, logical bunny to a fierce and ferocious warrior, complete with epic war cry.