Literally everything in Minecraft can get killed by you.
B
Baby Zombie
Baby Zombie Pigman
Baby Zombie Villager
Blaze
C
Creeper
Cow
Chicken Jockey
Cave Spider
E
Enderman
Endermite
Ender Dragon
Elder Guardian
G
Ghast
Guardian
Giant
K
Killer Rabbit of Caerbornoog (Killer Bunny)
M
Mutant Skeleton
Mutant Zombie
Mutant Creeper
Mutant Enderman
Magma Cube
S
Shulker
Skeleton
Slime
Silverfish
Spider
Spider Jockey / Spider Jockey (Wither)
W
Wither
Wither Skeleton
Witch
Z
Zombie
Zombie Villager
Zombie Pigman
