How is it a deal breaker? The side b thing.... Essentiall it'll take the same amount of start-up as Captain Falcon's Falcon Punch... which is a lot mind you. In I believe all forms of brawl (v, minus, plus, M) Falcon's punch and Ganon's punch I believe have the longest start up and highest knockback (I believe Ike's either is up there as well.) But its not that big a deal to me.
How about this... to make it interesting.
It will roll a % chance for a critical hit. If its critical... it'll do one of 3 effects:
1: Eat your shield (basically you cant block it but if you do you... your shield breaks)
2: Double Damge/Knockback
3: Unblockable with normal damage
If you're still against the unblockable part, then its no big deal with taking it out.
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Edit:
I'm also not sure how his counter would be over powered? It has no kill potential if you strike with it. And if you only use it to dodge, you're placed into the air... Having the option to hit makes it over powered?
His side-b being slow isn't the issue. An unblockable attack or even an attack that entirely eats your shields is completely unbalanced unless it was twice as slow as ganons N-B.
I said before that the counter sounds overpowered and that if you could make it fit without being retarded advantageous then its fine, I just wanted to make sure you understand that because pokemon brawl is going to be balanced we will change anything on any PSA to fit better.