Nut up and leave their ass. This sounds harsh, but in my experience people dont change until they have to contend with the harshest consequences of their actions.
They’ll cry crocodile tears and promise that they’ll do better from now on and to just give them one more change and everything will magically be better.
Maybe they put up an act for a bit but it always goes back to square one.
Stop tolerating abuse just because you love them or are afraid of being alone again. You are partially complicit in this by deciding to continue the relationship.