I was talking to a friend about this, and he and I both agree that Askai, when he was first released was way to powerful from the get go. Sure he has his weaknesses, but his pros are too damn good.
What other cards to you consider broken/imbalanced?
Spyke is pretty strong? No, it's stupid Overpowered against certain hands and disables Ambre effect. Really, just a pain to face in Standard or Extended.
Newer Cards, Kalindra is just annoying. Really, stalling games in Standard and Extended, and triple old then use all your pills on Kalindra. Really, it's pretty annoying.
Beeboy, the man who adapts, amazing card. But really... 7/7 with +2 power and copy opp bonus is pretty unnecessary, but whatever. He's just fine as he is, if you asked me.
Those are just my opinions on some newer OP cards.