kill
murder
slay
destroy
waste (informal)
do in (slang)
take out (slang)
execute
massacre
butcher
slaughter
dispatch
assassinate
eradicate
do away with
blow away (slang, mainly US)
obliterate
knock off (slang)
liquidate
annihilate
neutralize
exterminate
take (someone's) life
bump off (slang)
extirpate
wipe from the face of the earth (informal)