Synonyms of rub someone out in English:

kill, murder, cause the death of, end the life of, take the life of, do away with, make away with, assassinate, do to death, eliminate, terminate, dispatch, finish off, put to death, execute

slaughter, butcher, massacre, wipe out, destroy, annihilate, erase, eradicate, exterminate, extirpate, decimate, mow down, shoot down, cut down, cut to pieces

put down, put to sleep

bump off, polish off, do in, do for, knock off, top, take out, croak, stiff, blow away, liquidate, dispose of

ice, off, waste, whack, scrag, smoke

literary slay