No, there's no specific way to critical finish differently with Yoshi. I know this because of training mode.
I set the training dummy to "all guard" and proceeded to critical finish. And the messages you get are random.
There's:
A heart one. He says, "Waah?! This cannot be!"
A fart one. He says, "Shame on thee!"
A Soul Calibur one. He says, "Heaven awaits!"
A red confetti one. He says, "That's it! That's it!"
A purple thunder one. He says, "Na-mu..."
And no kanji one. He says, "Great misfortune."
In any case, this is basically day one stuff or so. However, this thread might get closed because not many(including myself) like clutter threads. This does not mean I(for instance) am trying to shoot you down. Aside from that, is there anything else you're curious about regarding Yoshimitsu? I along with my Yoshi hardcore buddies will try our best to help. Just PM one of us, and we'll get to you.
-NamuSkull
P.S. Dost thou wish to challenge Pocky Yoshi?
