When listing the best fighters Royce defeated, names like Shamrock, Severn, and Pat Smith (Sabaki champion) are likely to come up first. Unfortunately, this bypasses the fighter who probably ranked third--after Severn and Shamrock--in greatness: Minoki Ichihara.
That forgettable little guy from UFC 2 that Royce wiped out in the opening round was one of the most successful Daido Juku fighters of the early 90's, finishing first at heavyweight several times. Daido Juku is a form of MMA with fewer rules than shootfighting, and was around since the early 80's. It combines Judo and Kyokushin, but with "space helmets" to permit facial strikes and headbutts.
You can see a bit more of it here: