Intending to entrap; alluring but harmful.
Hansel and Gretel were lured by the witch’s insidious gingerbread house.
Treacherous.
Producing harm in a stealthy, often gradual, manner.
The battle was lost due to the actions of insidious defectors.
Secret; surreptitious.
Done by moving the hand (and arm) from below.
Sly, dishonest, corrupt, cheating.
Insincere; sarcastic.
An underhanded compliment is actually criticism.
His underhanded trick backfired and he was disqualified.
Understaffed.
Devious people, collectively.
In an underhanded manner.