ghaleon I think you're approaching this whole thing the wrong way man. I don't think you're going to accomplish shit by adopting such an aggressive attitude towards the guy. There is literally no upside to you beating the shit out of him, regardless of whether or not he has his life together. You married his sister, you've got to deal with this guy for the rest of your life bro. Or at least that's what it looks like on paper.

There is literally no way something like that would just blow over, even after many years have passed.

Basically you can:

1) clench your teeth and deal, and count the minutes till the guy leaves town... like pretty much 99% of people would do in a situation like this

2) talk to the guy about it, without getting all pissed off, and just make it clear that what he did was too much and won't be tolerated in the future. this won't work without you apologizing for vaguely threatening to kill him however.

the best outcome for you would be that this dude does get his life together and some time down the line you may build some kind of marginally positive relationship with him. yeah there's very little upside, but it makes little sense to preclude any chance of it ever happening. weird as it sounds, you should actually be rooting for the poor guy.