CONTEXT: (Avoid reading if this ruins the video for you)
The plot involves a reactor exploding or something, and Captain Falcon chooses to stay behind and punch the bad guy one last time rather than escape. They both get vaporized in the blast. The explosion is from the reactor/whatever, not the punch. Yeah, I made that mistake too when I first saw this and learned what was really going on after digging through about 9,000 Youtube comments.