Shoot Pool, not people
Agreed. Looks like we interpreted the thread title differently. I took the word "powerful" literally, and DeLuna has the most powerful break that I've ever seen. If the question is to be interpreted as who has the most effective break ever, I think I'd have to go with SVB, but all the guys you mention are very much in the conversation.
Strictly on power I would put Kucharo and Breedlove on top of the list. Yes, even over DeLuna. Jeff would have been in awe of Jon's break I'm sure.