sucker

cat's-paw, mark, target, victim

butt, derision, laughingstock, mock, mockery

booby, dodo, fool, goose, half-wit, jackass, lunatic, monkey, nincompoop, ninny, nitwit, simp, simpleton, turkey, yo-yo

loser

blockhead, cretin, dolt, dope, dumbbell, dummy, dunce, idiot, imbecile, moron

groupie

admirer, amateur, collector, connoisseur, dilettante

authority, expert

adherent, convert, cultist, disciple, follower, hanger-on, votary

advocate, apostle, backer, champion, evangelist, exponent, friend, patron, promoter, proponent, supporter

partisan (also partizan), zealot

booster, rooter, well-wisher

faddist