Is it permitted to take revenge when the other keeps his negative behavior, relying on "immunity"?
Let us take example to understand well things. Mr T and Mr R are neighbors. Mr R is an evil and hypocritical rasha, and will never ever do a good action to Mr T. Especially, when T asked to borrow something, R always refused (let's say this occurred many many times). But, frequently, Mr R brings his honey fake smile and knocks at T's door to borrow things (let's say he brings them back OK). This is causing chagrin to Mr T to be abused by his enemy, who knows he will keep his disgusting behavior towards him, and relying on the fact his kind neighbor is yere shomaim.
But what to do? If he refuses, does he transgresse issur neqima? Or even if he just became angry and shows the rasha he is not duped, does he transgresse issur netira ?
Seems obvious Tora doesn't ask from us to be naive and abused. But is there clear limits in posqim etc?