noun
parasite, leech, toady, flatterer, fawner, hanger-on, toadeater, tufthunter, lickspittle, flunkey, adulator, timeserver, cringer, crawler, truckler, slave, puppet, cat's-paw, groveler, spaniel, lap-dog, sniveler, apple polisher, gofer, yes-man, bootlicker, brown-nose*, stooge, back-scratcher, flunky, smoothie, soft-soap artist, baloneyer, apple-saucer, doormat.
Antonyms ruler*, master, dictator.