I really suggest use EV reducing berries to drop his/her EVs to zero( you get them in the Dream World if I'm not wrong).
Then train it in Attack and Speed.
But seriously. It's useless. So I don't recommend training it. Maybe trade it for a useful Pokemon.
Just look at its base stats(as Lopunny) -
HP-65; Att.- 76; Def.-84; Sp. Att.- 54; Sp. Def.-96; Speed-105