Estropeé comes from the verb estropear, which is a highly expressive Spanish word meaning to ruin, damage, or completely spoil something.
In the remix, Romeo Santos confesses, "Reconozco cada falla, estropeé tu corazón" (I recognize every flaw, I ruined your heart). Instead of using a common verb like romper (to break), he chooses this evocative word to dramatically admit that his selfish behavior caused profound, lasting damage to the relationship.
This song is a fantastic back-and-forth between two ex-lovers who are finally being honest. Natti Natasha kicks it off by telling her ex he never got to see her at her best. Why? Because, as she puts it, "siempre me frenaste con tu pésima actitud" (you always held me back with your terrible attitude). She says she lost herself trying to love him on his terms, but now she's done. She's found her strength and is "Disfrutando la mejor versión de mí" (Enjoying the best version of me).
Then Romeo Santos, "The King" of bachata, jumps on the track to give the man's side of the story, and he completely agrees with her! He admits he was a mess, blaming his "complejos de ser rey" (king complex) for ruining their relationship. Now the tables have turned, and he's the one suffering. He sees how amazing she is without him and regrets everything. He even has a great line where he complains he has to "Termino en un remix sufriendo por perderte" (End up on a remix suffering for losing you). It's the ultimate musical soap opera: she's thriving, and he's realizing exactly what he lost.