Here are three very bad choices for this list IMHO:
Brandon Slay- first, he beat the GOAT freestyle wrestler, in a legit way, not based on some obscure penalty point when the guy was almost 40 years old. He blast doubled him to the mat multiple times. Second, for whatever reason Slay was an entirely different wrestler that year. He also beat Joe Williams who would have likely come home with a medal at that point imo. Williams barely lost to Satiev himself in 1998. Had another super impressive win to make the final at Olympics I believe but cannot recall the details but maybe someone else can recall the credentials of who he beat in the semis. As for his loss to Leipold, man was that screwy. This was back in the old upper body clinch era, they could give you a two point penalty on a whim for not letting your opponent get the best lock possible on you, and that's what happened here. Then, they call Slay for grabbing fingers. Two completely subjective penalties put him in a 3-0 hole. That may not sound like much, but in an era where takedowns were one point, there was no pushout, and against a true defensive specialist, that was a hell of a whole to come back from. I honestly felt like the match proved absolutely nothing other than the idiocy of FILA. If he would have kept going I'd bet that he would have took home more world medals, he was a force at that point.
Kerry McCoy- only took home one world medal, but was always a top contender he just never seemed to put it together at the right time. I'd guess he's beaten a half dozen or more World Medalists. Hell he kept two off the team right here in the USA including Stephen Neal, and in 1996 he was a hair behind Kurt Angle to make the team at 220.
Jamill Kelly- Just a completely different wrestler in international freestyle than he was in college. Made the team twice over some VERY stiff domestic competition including Lincoln Mac and Bill Zadick in his prime.
If the category is the more positive, "who came out of nowhere" as opposed to "worst", I'd say:
1. Eggum (a country Mile behind Cael and I don't think he was ever even our #2 guy other than this year).
2. M. Zadick (always a stud domestically but his style did not result in many high level wins other than the improbable run where he knocked off Batirov, amazing)
3. Gilman (within a point of elimination at the last chance qualifier to world finals, amazing)
4. Tolly Thompson (never beat Kerry McCoy outside of one time in college that I recall but wins a World Medal in his one shot whereas Kerry tended to fall a bit short most years).