[@Goliah]
I have an idea but the GM's would have to approve it. We could add it to the lore that Luthor infected all of the Kryptonians on Earth with a disease that dulled their powers. It could have brought them down to the level Superman was at when he first appeared in comics. Basically as strong and fast as a train, can jump really high, and impervious to anything smaller than an artillery shell. Your character would still be really strong, but manageable. The disease idea would also explain why the Kryptonians retired with everyone else instead of just continuing their work— without being the strongest ones anymore, it'd be too dangerous. I don't know how you could explain a relationship between Supergirl and Taskmaster though...