A friend of mine had an abusive stepfather. He mostly beat his wife, until one day he threatened their baby. That night, my friend's mom shotgunned the stepfather in bed.
Would putting him jail forever have been better? Sure. But it wouldn't have happened. He'd have been thrown in the drunk tank overnight and be back at it the next morning. If she'd divorced him, he would have fought for custody.
She solved the problem forever. I can't endorse what she did, but I also won't judge her.