One question: does the "never be healed for at least 20 consecutive battles in Mt. Battle" take the automatic healing after every battle into account? Aside from that, accepted!*Woops..colosseum, not XD...
Anyways, change it to ImTooCute the Ledian (Cipher Peon Kloak, The Under).
This Ledian realised, ever since Game Freak made, that it was a crappy competitive pokemon. It's only redeeming feature was that it was remarkably cute for a bug pokemon.
As a result, ImTooCute can never use any contact moves, as people can't appreciate how cute a pokemon it is if it's too close.
Also, it can never hold items, as they distract people from Ledian itself.
Oh, and Ledian cannot be on the field at the time you attempt to snag a Shadow Pokemon.
Add to that, Ledian must lead and never be switched out and never be healed for at least 20 consecutive battles in Mt. Battle, not including the first 10 which are mandatory.