Sorry I forgot that.I use attacks that are not very effective. After he uses Cosmic Power enough times, by then he KOs my level 93 Gallade with False Swipe, so I'm stuck with level 100s. Luckily, if it's not critical hits, they do less than half damage. With Critical Hit, it ignores boosts in defenses, so it's OHKO...
I have been catching ALL legendaries using regular Poké Balls as of a couple years ago. While Capture O-Power level 3 makes things a little easier, it's still difficult to do. This is all while soft resetting until I get IVs I'm satisfied with.
I've said I use False Swipe.
Your Gallade runs Swords Dance?