I actually Ichigo's little bankai makes it more climatic than those big beasts. There was such a huge build up to it, and you'd think the bankai would be something enormous. When you see that it's just a little sword, you expect him to be super strong. It's like Vegeta back when he first appeared in DBZ - the little guy is always super strong. Surely, all that "power up" couldn't have been for nothing.