untrustworthy

Synonyms: capricious conniving crooked deceitful devious dishonest disloyal dubious fair-weather faithless false fickle fink fly-by-night guileful irresponsible questionable shady sharp shifty slippery sneaky treacherous tricky trustless two-faced two-timing unassured undependable unreliable unsafe unsure untrue untrusty

Antonyms: dependable faithful honest reliable trustworthy