Surprised no one has mentioned legendaries... and I have the perfect one.
Deoxys Attack.
I mean, now you're gonna say that it has amazing stats in Attack and Speed, but look at the other side.
50/20/20 defenses. Magikarp has higher than that. Sunkern outclasses it in its defense, just lacking the HP. At least sunkern can actually tank a knock off. Not this.
I mean, even Deoxys-Defense has SOME attacking stats. The other Deoxys Formes outclass it by far, and the only thing it has is a high attack.
Why not just use Mega Garchomp? It has an almost equal attack stat, and it has a larger movepool. Just putting it out there, Deoxys-Attack is horrible.