User blog comment:B214/Question and Answers 6/@comment-190.164.227.239-20161201033222/@comment-1359322-20161205013215

Well for all we know Belzard, the strongest Boosted Gear user, may be stronger than Vasco and Strada. In that sense, Ise would still shy from the strongest.

Though i think the reason why Ise is called weakest is because he became a Devil while the others remained humans. In a sense, it wouldn't be fair to view them at an equal platform.