Don't even get me started on Mega Medicham...... I don't even... it's just.... what have they done? It kind of looks like a psychic (Makes sense) mixed with a genie mixed with those people that raise snakes out of vases. I actually like Medicham, but for the sake of my eyes, I will never mega evolve it.
Mega Manectric isn't that bad, but it does need more work. It's almost just a lightning bolt. Not even a cat/dog thing (not sure wish it's supposed to be....).
And the worst of them all.......
Mega Banette....
It looks like its guts are popping out of it, the way they made it look like it could be zipped open/closed. I never particularly liked the way that it looked, but now.... it's just.... bleh....
Some others that aren't horrible but are pretty bad include: Pinsir, Aerodactly, Heracross, Gyrardos, Abomasnow, Gengar, Aggron, Mewtwo X.
I think Houndoom looks the best, to be honest. Lucario is pretty awesome, too.
I only like: Houndoom Lucario, both Charizards, Mewtwo Y, Scizor, Ampharos, Tyranitar, Blaziken, and Absol.
I wanted a Mega Dragonite, but it didn't happen. (Dragonite's my favorite pokemon). (Houndoom's my second.)