> I work with a colleague that doesn't compile/run the code before putting up a MR. I informed my manager who did nothing about it after he did it several times (this was after I personally told him he needed to do it and it was unacceptable).

At this point what you need to do is stop treating compiler warnings as errors, and just have them fire the shock collar.

Negative reinforcement gets a bad rep, but it sure does work.