>>45576942Tough Claws could work instead of Unburden, but I doubt they'd change it AND swap its stats. Plus, give it Belly Drum and a Sitrus Berry to hold, and you can make a lot of use out of Unburden.
Otherwise, I cannot think of any abilities that may work to make it a better Special Attacker. Maybe Berserk or a Grim Neigh clone?
