This is the *second* time I've come across surprisingly good

reincarnation-verse fic while looking for porn.

(apparently the title character limit is too short)

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"before they convinced you life is war", by EclipseWing. Harry Potter characters reincarnated into a more-or-less X-Men universe: if you had magic in the old world, you get a mutant power in this one. Amoral read-write empath Tom Riddle and (initially) reluctant mind-controller Harry Potter must team up to escape the re-education facility they're trapped in and survive in a mutant-hating world, despite remembering enough of their respective past lives to be well aware of their status as mortal enemies.

It's a little unpolished, but mostly just in a "probably didn't have a beta" way, and the plot is intriguing.