Riley Smith is a 5’9” two-foot dunker with a 50 inch vertical and a background as a professional football player.
Fifty inches at 5’9” is one of the highest verticals on this site relative to height, and the football background is not unusual for that. Several of the biggest verticals in dunking belong to athletes who came from track, volleyball or football rather than from basketball.
Dunkademics has filmed him twice, and both times the video was built around the same number — the max vertical, measured on camera. That is unusual. Most dunkers get filmed for what they can do at the rim; Riley Smith gets filmed for how high he leaves the ground, and the footage exists largely to settle the question for anyone who does not believe it.
He goes up off two feet from a right-left plant.