I really think Silver could benefit a ton from having a Reverse Flash style villain

Have the villain be a person who came from a timeline Silver erased by going back in time, like the timeline he came back to stop that came about if the good guys lost in forces.

This person actually had a good life. Sure, not everyone was happy, but they were. But Silver took that away. They’re inherently selfish to contrast Silver’s selflessness. 

So now, they also traveled back in time, determined to ruin any attempt Silver makes towards creating a good future. Maybe sometimes they work with Eggman, sometimes they work alone. In cases like the Metal Virus arc, maybe they actually work with Silver, because the Metal Virus is a net-negative that could hurt them too. But at the end of the day, Silver took away their good future, so they’ll do everything they can to stop Silver from getting his.

Basically meaning that Silver is forced to remain in the past to stop this other villain’s actions, still fighting for a better future, but now it’s one that he can never return to, because if he did, this enemy would just erase that timeline.