croak

beef, bellyache, bleat, carp, caterwaul, complain, crab, fuss, gripe, grouch, grouse, growl, grumble, grump, holler, inveigh, kick, moan, murmur, mutter, nag, scream, squawk, squeal, wail, whimper, whine, yammer, yawp (or yaup), yowl

check out, conk (out), demise, depart, die, drop, end, exit, expire, fall, go, part, pass (on), pass away, perish, succumb

carry off, claim, destroy, dispatch, do in, fell, kill, slay, take

assassinate, bump off, dispatch, do in, execute, get, liquidate, murder, rub out, slay, terminate