Pernicious – Having a harmful effect, especially in a gradual way
The perm was vicious (pernicious). The perm gradually worked its way around the back of the woman who was verbally attacking her, and was going to harm her.
Examples of pernicious in a sentence
The pernicious cycle of abuse within their family must be stopped.
Because she hates me, my neighbour is always spreading pernicious lies about me.
Jake’s pernicious behaviour is going to put him in the hospital one of these days.