There isn't a lot of Dark!Poe I noticed. So, what if Poe is a high rank official in The First Order. One day, FN 2187 save Poe from getting assassin. Poe couldn't help it feel fascinated with FN 2187 which slowly become a obsession, and possessive of him. FN 2187 is frightened of the situation that he is in.
+Poe still end up naming him Finn.
+FN 2187 escaped The First Order but got caught by Poe.
Dark!Poe/Finn - First Order AU
+Poe still end up naming him Finn.
+FN 2187 escaped The First Order but got caught by Poe.