Forward Smash needs better hitboxes, a lot better knockback and damage and it could look a little more powerful to. It's a cool looking move, so I want him to keep it. But it should act like Mewtwo's main finisher I feel. Down Smash same way. It needs the raw strenght to cover up for the fact it doesn't hit at two sides. Up Smash is easy to buff I feel, just make all the hits connect better, and make it much faster.
His tilts are quite good, but they should get rid of the sweetspot with so little range. Make his tail equally as strong everywhere.
As for his aerials: improve N air so that it does more damage and make the hits connect better. F Air needs more range, U Air and B Air are actually fine, if they could give him a new B Air that'd also be good I feel. But D Air needs to be stronger, or faster. Definitely improve hitboxes all around though.
One handed Shadow Ball would also be wicked yes.