I won't let you get away with itAn informal threatening expression meaning that the speaker will punish, confront, or otherwise deal with someone. It is a shortened form of 가만히 안 둔다, literally “won’t leave [someone] alone.” The person being threatened is often omitted or marked with 를.
KO: 또 그런 짓 하면 가만 안 둔다!
EN: If you do that again, I won't let you get away with it!