Goku after "fighting" that one guy Beerus hired to keep him motivated.

Like, canonical? No, there was Goku Black but that was another using him has a skin suit It wasn't really Goku.
Fan made tho? Pfff yeah of course there are, you can't watch a dragon ball video on YouTube without getting at least two or three videos with an edgy Goku on the thumbnail titled "What If Goku was betrayed and then X happened" recommended to you on the sidebar, I watched a couple of them and as expected they had playground level writing things like: "and then Goku in super saiyan god super saiyan mastered ultra instinct omega mode killed them all with the god of destruction powers".
MasokoX from TeamFourStar has a few good "what if" stories but none of them are straight up a "what If Goku was evil?" (most are about the opposite villains turning good), off the top of my head tho he did make one where Goku wins one of the early tournaments and instead of being humbled like in canon he becomes kind of a prick and that has long lasting consequences for the rest of the story but even in there he never goes full on evil.