Yeah attack speed bring Chichu to the top in terms of commando's, but some people through monster infusions have built up Omega in such a way that his attack speed is greatly increased (he is very slow otherwise) and this makes Omega the best commando in the game
But you'll have to level up several other monsters, then infuse them into omega to get that. As the game isn't difficult I won't be going to that trouble; the monster system is excellent, if only the game was hard enough to make me feel that I wanted to make the "ultimate" monster.