Other forms: fulsomest
Compliments usually make you feel pretty good, but fulsome compliments, which are exaggerated and usually insincere, may have the opposite effect.
Hundreds of years ago fulsome used to mean "abundant," but now it's more often used to describe an ingratiating manner or an excess of flattery that might provoke an onlooker to mime gagging. If you find fulsome to be a rather clunky word, there are several fun (if vaguely stomach-churning) synonyms, including buttery, oily, oleaginous, and smarmy.