Yo Malamar is actually pretty good. Topsy Turvy to fuck up boosters, especially calm mind and Swords Dance users. Super Power is a no brainer. Psycho Cut for coverage and STAB.
Then this is where he gets interesting. You can give him swagger to combine it with Topsy Turvy to cripple foes (which I've been doing), or you can let him be a counter to Aegislash with Foul Play. If Aegislash uses King Shield, its a boost for Malamar. If it uses Swords Dance, its very good damage for Malamar.
He's kinda underrated IMO