Just found this short manga about the classic setup
>MC is getting cucked by Bull
>Bull also has girlfriend
>MC and Bull's GF team up to get revenge on them
>End up falling for each other along the way

https://mangadex.org/title/5f11b455-4d6a-49c9-828e-118395bd8547/kanojo-ga-senpai-ni-ntr-reta-node-senpai-no-kanojo-wo-ntr-masu

Was a decent little read. Only problem is after the big reveal, the cheaters have a little melty and it's strongly implied the MC and FMC start dating, but there's no epilogue to show the fallout of the cheaters' actions or the new happy couple. Literally needed like, one more chapter to properly wrap things up. That, and tie a few loose ends.

Still, another case of shitty people getting what they deserve in the end.