>>31880467People often describe these moves as being ways to 'punish' your opponent for over-committing energy to a Pokemon (e.g. attaching more energy than necessary to secure a KO with Thunder Lance). The problem is that this view inevitably makes some cards essentially unusable. Pokemon with high energy costs cannot be used as you will be 'punished' merely for attaching the energy required to attack*.
Attaching energy in order to attack is a fundamental part of the game, so I don't really understand why they keep making X Ball/Evil Ball/Energy Drive style attacks. The game seems like it will be slowing down in future to encourage more evolution (another fundamental aspect), but energy attachment is still going to be penalised.
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I'm not saying that these Pokemon would necessarily be good. They're generally too slow; Yveltal just guarantees they'll never do well. 