I can't believe how many people here are telling you to turn the other cheek. There's nothing wrong with settling a score, and there's no statute of limitations on doing so.

Yeah, maybe you're obsessed with him while he doesn't think twice about you. So what? Give him a reason to think twice about you. I think the idea here is to make him the beta; have him constantly thinking about you and how intimidating you (now) are, like you've been doing for decades.

The hard part is, of course, either a) doing this without anyone else watching or b) if you can't, then figuring out a way to make him look like the instigator.

If you can't get him alone, it's easy enough to get him in an oral confrontation. If he's smart enough to avoid the new more alpha you, it could be as simple as walking up to him and whomever he's with and saying something cryptic with a smirk on your face. Like, "Nice to see you. Good thing the boss let you get away for a few hours." Not that in particular, but you know what I mean. The guy's got to have some Achilles heel, something that he's sensitive about. Go deeper than that if you want. Make a reference to his criminal record, or that time a girl broke his heart, or his balding head, or something. Be creative.

It'll be obvious if you're getting through. If not, continue until you get a reaction. If you eventually hurt him enough that he wants to confront you later privately, that's your chance to drill him. If he's dumb enough to instead confront you in front of an audience, say something like "I know you're so big a jackass to ruin X's wedding." Implying, of course, that he's slightly less of a jackass.

Bait him into physical confrontation, but I'm saying this assuming that you can hold your own. Idiots and assholes understand only force, and that seems to be what your cousin is. Good luck.