Bowser is definitely very difficult for the melee characters (Simon, Ryu, Link). Link has some maneuverability, but Simon and Ryu are pretty much screwed if they don't have a long range sub-weapon and enough ammo to kill Bowser (protip: Daggers are amazing against Bowser ). It would be nice if something could be done about this, but honestly, I can't think of anything that wouldn't be cheap and unfaithful to the original games (such as giving Ryu unlimited small shurikens as a base weapon). I think the best you have to do sometimes is get hit and hope the invincibility frames give you enough time to reach the axe. Even Mario needed this strategy in the original sometimes. And if you get game over, you have a whole other shot at the world to gather power-ups again.