[MrZeropage]

ah ok, I see

then manually delete all best results from this user

execute the following query:
UPDATE games_list SET bestscore=0,bestmid=0 WHERE bestmid=UserID

replace UserID with the UserID of that deleted user
if you have some table_prefix set, remind to put it infront of "games_list" ...

After the query is executed, run the Score Tools -> Update Best Results again to fill up the empty slots with other users