Huh, 'Annabeth cheats on Percy' plots usually start with a breakdown in communication after the wars end. The peace leaves a vacuum where all their shared trauma doesn't have an outlet anymore, and they realize they don't know how to just... be. Annabeth gets absorbed in rebuilding Olympus or New Rome's architecture, Percy feels adrift without a clear enemy, and they just drift. The cheating itself is often with someone she works closely with—another architect, a demigod from a different pantheon in a crossover, maybe even a mortal who represents the 'normal' life she sometimes craves but can't have. It's less about passion and more about a quiet, desperate search for a connection that feels simpler.
Percy's apotheosis in these stories is rarely a reward. It's a consequence, sometimes a self-inflicted punishment. He might be offered godhood as a 'consolation' by a sympathetic (or manipulative) Zeus, or he might actively seek the power so he never has to feel that vulnerable again. The tragedy isn't that he becomes a god; it's that he becomes one to escape the pain of being human, which is the very thing Annabeth fell for. The godhood arc feels hollow, a shiny prison. I find the ones where he refuses it and walks away entirely are more cathartic, honestly.