Insidious
Part of speech: adjective
Definition: Producing serious harm in a stealthy, often gradual, manner. Intending to entrap. Treacherous. Describing a disease which worsens with few or no symptoms to signal its gravity. Describing a disease with subtle or gradual onset. Patients with insidious diseases oftentimes cannot point out a time when the symptoms began.
Example sentence: In recompense, envy may be the subtlest - perhaps I should say the most insidious - of the seven deadly sins.
Dangerous
Part of speech: adjective
Definition: Full of danger.
Example sentence: Part of the core information that I've been purveying is that identity politics is a sick game. You don't play racial, ethnic, and gender identity games. The Left plays them on behalf of the oppressed, let's say, and the Right tends to play them on behalf of nationalism and ethnic pride. I think they're equally dangerous.