Strongest? It comes down to the player. Certain characters appear to have a better arsenal from what we've seen but we all know how quickly that can change or be misleading. It'll be the characters we view and look down upon that'll kick us around and destroy us.
I'll personally be trying out every single character and whoever clicks with me, even if they aren't a favorite. I'll use them. At least if I want to win <3 hehe.
"Exit the stage. Your act is over." - Vergil
"Come on, come on, come on, come on, come on! Now die!" - Albedo