insidious formal
(something dangerous or deadly that seems to be harmless)
- They are trying to put insidious ideas in our minds.
- You don’t notice this insidious disease until it’s too late.
invidious formal
(unpleasant and likely to offend other people or make them jealous)
- The director never makes invidious distinctions between employees.
- It would be invidious to single out any individual.