How about a Supercorp Groundhog Day AU? Where Lena keeps getting hurt and Kara relives the day until she can save her? Or the other way around?
OH MY GOD WAIT LIKE
Picture Medusa, but things keep going wrong: the first time, Kara tries to stop Lillian too soon, and the bomb goes off, and all of the aliens in National City die as the fiery ashes fall from the missile. But when she wakes up and slowly, sadly flies to the DEO the next day, J’onn is there, alive, and everything seems to be happening all over again.
The second time, she shows up at the wrong place at the wrong time, and Lena gets shot, and Kara nods off while sitting next to her hospital bed, wakes up once again on the morning of Medusa.
This keeps happening, and she just can’t get it right: everyone around her keeps getting hurt. It is a dizzy balancing act of who will I fail next, and each day is another aching scar on her heart.
(I’m sorry, she wants to say. I’m so sorry. But they don’t remember, and explaining is impossible, and Kara knows this is her burden to bear alone.)