Steve Plasencia for the University of Minnesota has to be up there. He just got downgraded and is now on a year-to-year contract. The University of Minnesota is the only D1 school in a very good running state, so he gets probably 4 out of 5 of the top guys in the state each year. He's turned multiple state champions(~9:00 3200 guys) into over 9 minute 3000m guys. Absolutely laughable. With the guys they get out of high school, they really should be a podium contender in cross every year. Also, completely forgot to mention that he let his own kid on the team(77th at state cross his senior year in a 16:52) over guys in the top 20 who were also in the 4:15/9:15 range on the track. WOW.
To be fair he has had some success. One of his athletes won the ncaa steeple title last year, which is more then most D1 coaches can say.