I feel like this is the one of the few games where it is very plausible to have a Manipulator route where the MC firmly holds the reins of this debauchery. In this route he realizes very early that Liz is cheating on him, is hyper outraged and wants revenge on both Liz and Matt, and teams up with Richard to ruin their lives. On one hand MC strings Liz along with fake affection, and on the other really pushes her deeper into the abyss behind the scenes. One method I can think of is innocently saying that egoistic men who thinks the world about themselves (like Matt) cannot stand it when someone else butts into their plan and goes after their prey, essentially suggesting to Liz that she should hook up with more men. Matt falls for it hook line and sinker and it seems like the plan does work, but you actively sabotage both Liz and Matt at every turn so that things always spiral out of their control and imagination.
Like for example Liz only wants to pretend to hook up with a guy but ends up actually blowing him against her will because reasons; or she goes to a shady bar to snap some convincing photos for her top secret (not) sharespace that Matt will see but ends up being fucked by men. Matt is angry and suspicious from all the men that suddenly popped around Liz and takes it out on her plus upping his ante, but that makes him sloppy and allows you to screw with him even more. Richard is angry on your behalf and goes along with your plan to slow drag both Liz and Matt into hell with his supernatural hacking skills. At some point Richard can even get some of that Liz, like when she blacked out after getting fucked and he uses the opportunity to fuck her in addition to creating more incriminating evidence/blackmail material yada yada under your orders.
You can even drag Sam into this because technically none of this would have started if she didn't leave behind a drunk Liz to fuck some sleazy guy, which you find out one half thanks to Richard's help and another half because your brain is actually online for once. Like oh you're so worried about Liz, then why the fuck didn't you protect her the first and most important time?
As for ending I can see two ways: one you still remain with Liz after Matt is ruined/defeated/imprisoned, but not because you love her. It's because you want to ensure she will never be free from this life even after Matt is gone, and you will be there to savor it every step of the way. And the other ending is you breaking up with her and letting go after fulfilling your vengeance, and somehow she ends up with Richard (would both be hilarious and bodes ill for Liz because Richard knows she's a cheater and a whore). Happy ending(?).
