>>41662087If you're playing SS you're out of luck, but in any of the Gen 6 and 7 games (and Pokémon Showdown) her mega is extremely overpowered, with pretty good defense, attack, and the most important thing: Huge Power as an ability, which doubles her attack stat.
Her competitive moveset tends to contain Sucker Punch, Play Rough, Swords Dance, Stone Edge and Fire Fang.
Again, if you're not going to mega evolve her (or can't, thanks gen 8), then she's really useless in competitive sadly.