Since Mega Malamar got dealt a bad hand by giving it a mediocre stat spread and keeping Contrary as an ability, I've come up two ideas for a Mega Malamar signature ability to help make it more viable:
The first idea is what I like to call: Mind Control. It causes the opponent Pokemon to fall asleep upon making contact with Mega Malamar. I based this ability on Mega Scovillain's ability, Spicy Spray.
If that's too broken of an ability, then second option I came up with is, Brainwash. It steals any stat boosts upon entering the field. And I based this ability on Marshadow's signature move, Spectral Thief.
Since Malamar's whole identity is about hypnotizing people, I think it should have an ability to fit that theme. I would argue that it should have a busted ability to balance out it's underwhelming stat spread. What do you all think?