It's taken me an extremely long time to finally capture Mewtwo. It was able to wipe out my entire team for approximately five or six times, which, if you ask me, is a lot! At the time I was battling it, many of my Pokémon were ten to fifteen levels higher than Mewtwo, but it still managed to have them taken down. And it did it without even breaking a sweat. I've done all sorts of stuff trying to capture it—paralyzing it, getting its health down to as low as possible, putting it to sleep, and more. Nothing worked, though. None of it. d: I've tried using a variety of Poké Balls trying to have it caught, but the only one that was ever close to capturing was an Ultra Ball. Then, I've realized that Mewtwo was in a cave, which is dark. And Dusk Balls have a significant capture rate when used in dark places. Since I didn't have any of them in my backpack, I decided to exit the cave and buy myself some. When I was done, I've returned to the place where Mewtwo was in and re-battled it. Finally, after the use of only twenty to thirty Dusk Balls, I was able to get my hands on Mewtwo successful. If I had thought about this sooner, then I would've caught Mewtwo a long time ago.
Currently, I have this Pokémon stored in one of my PC boxes. I would have had it on my team, but since it's banned in competitive play, I decided not to. If I did, then a lot of people would've complained when battling online. xD"