One that I haven't seen so far:
Lucario. Sure it is a great pokemon, with good stats, a diverse movepool, and a nice typing that allows it to take some hits in-game, but it has a bad STAB movepool. In BW2, when I used one, I grinded in the battle subway for quite some time because I didn't want to be stuck with Force Palm almost all game for its only STAB (it learns its first better STAB moves, Close Combat and Aura Sphere, in the 40s). XY gives it Power-Up Punch, but that isn't so great, either. For its other STAB, Steel, it gets nothing. That really holds it back in-game.
Don't forget that Lucario isn't incredibly fast, so it might take a hit after it Close Combats. And all its STAB moves have low PP, causing you to need frequent Elixirs or visits to the pokemon centers.
Lucario. Sure it is a great pokemon, with good stats, a diverse movepool, and a nice typing that allows it to take some hits in-game, but it has a bad STAB movepool. In BW2, when I used one, I grinded in the battle subway for quite some time because I didn't want to be stuck with Force Palm almost all game for its only STAB (it learns its first better STAB moves, Close Combat and Aura Sphere, in the 40s). XY gives it Power-Up Punch, but that isn't so great, either. For its other STAB, Steel, it gets nothing. That really holds it back in-game.
Don't forget that Lucario isn't incredibly fast, so it might take a hit after it Close Combats. And all its STAB moves have low PP, causing you to need frequent Elixirs or visits to the pokemon centers.