A universe filled with AUs who are free from judgment from their canon-abiding brethren. In this verse, we've picked up canon and tossed it straight out the window! Take that, canon.
What if Peter Pettigrew hadn't escaped at the end of Prisoner of Azkaban?
At any rate, dear Tom was successful at recombining the remnants of his soul. The manner in which to do this is to repent for his cruelty and heinous acts by experiencing the feeling of true remorse.
Alas, Tom Riddle did not appear to have a shred of humanity left in him.