User blog comment:Fliu/Chapter 935: Disaster at Udon/@comment-25654036-20190308093055/@comment-3507581-20190408232625

Also, remember when Blackbeard nulified Whitebeard's DF? Whitebeard still pushed him to his limits and could have killed him if not for you-know-who...

If Devil Fruit users learn to fight naturally, then seastone and the Yami-Yami no mi would no longer be much of an issue.

Check "Brought down to Badass" and "Boxing Lessons for Superman" on Tv Tropes.