User blog comment:CrimsonFlame2K/Ask Crim's characters!/@comment-995908-20180724221705/@comment-9749276-20180725081227

Whirlwind: "I've come across a lot of tough guys over the years - Knuckles with those atomic fists of his, Shadow and his potent control over Chaos Energy, and Zagan's sheer brutality in his swordsmanship. But my toughest fight by far was with him... and not just in terms of physical prowess..."

(I'm sorry, Ryu, but revealing this person's name would be a major spoiler for one of my stories.)