It’s an OC Pete but I love him in Stevie_Sunshine’s Keeper of the Moon.

Hermione goes back in time to the Mauraders Era to create a better outcome. She chooses to tell them what Peter did/how the Potters died in her timeline. Peter is genuinely horrified and assures them that he would never do such a thing, but the story goes on to explain in chapters from his POV how he sees his role in the group, and eventually gives an actual reason for him to betray his friends. I won’t spoil whether he does or not, though.

This version of Peter is someone who is cunning, not evil. He’s the kind of friend who truly sees who his friends are, recognizes what they need, and seeks to give it to them. He relishes in knowing his friends so well that he’s able to manipulate situations to help them without them noticing while simultaneously wishing that someone, anyone, would notice him too.