The "Young Avenger" power name is so on the nose it's kind of painful. Not a complaint, just an observation.
Seems to fit the character, even if I can't specifically remember when he did something like that... but I find Speed kind of forgettable in general, to be honest...
Yeah, I'm definitely strongly against outside powers modifying special attacks (even if they're on the same card). No problem with extra dice being subtracted, though - it's a loophole, but it's more of an addendum to the attack than a true modification.