Literally there's a lot of ways to get back at Ari if he just wants to prove a point that haesoo doesn't have "nothing". Like one thing I could think off that's satisfying is maybe take haesoo out on a dinner date and have her dress up (complete makeover with luxurious things etc) and make sure Ari sees them together.
But I think he did this on purpose because he's petty as hell lol and I think, for him, this is just one of the necessary steps he has to take to slowly creep in minshits life for his revenge. Like literally he's hovering on the things/people surrounding minshit

As much as I love taeha and how he put Ari in her place by showing her that Haesoo has something she doesn’t I feel like he should have let Haesoo at least take care of this sort of thing. If Ari tells Haesoo what happened it’s only gonna cause more conflict between the two of them.
But I am really proud of him for doing this for haesoo. I just wish he would have at least taken a different approach then the one he did