How about a crossover of Final fantasy VII with Sephiroth as the main character? You can decide how he gets to Equestria. A few suggestions if you cant think of any, he loses his memory and re-discovers it throughout the story, while fighting cloud, a portal opens up from the force they produce with their strikes and sucks Sephiroth in. If you go with the first suggestion, you could make him seem like a good guy and when he discovers his memories, have him debate with himself if he should stay good or go back to evil. If you go with the second, have his normal personality but make him cooperative because he would want to return to his world. You can decide if he back stabs the ponies afterwards or his morals change.
How about a crossover of Final fantasy VII with Sephiroth as the main character? You can decide how he gets to Equestria. A few suggestions if you cant think of any, he loses his memory and re-discovers it throughout the story, while fighting cloud, a portal opens up from the force they produce with their strikes and sucks Sephiroth in. If you go with the first suggestion, you could make him seem like a good guy and when he discovers his memories, have him debate with himself if he should stay good or go back to evil. If you go with the second, have his normal personality but make him cooperative because he would want to return to his world. You can decide if he back stabs the ponies afterwards or his morals change.