I was just making a fun list of guys who started out as TKDist who found success in other fight games. I can think of Troy Dorsey who became boxing and kickboxing world champion, top boxer from the 90's Skipper Kelp lists TKD as his hobby on his old boxing card. I am sure a lot of old full contact PKA legends had their roots in TKD, hope you can add to the list:
Troy Dorsey
Skipper Kelp
Troy Dorsey
Skipper Kelp