Hmm, well if you are going to enter horses in the discussion, then I'm going either Mother Nature or Father Time. Both undefeated and untied. Where as Secretariat lost a couple of times. I don't know I think probably there is some downhill snow skier who should be considered as World class downhill is the toughest thing to do in the world of sports being that you are on the edge of death. No, hitting major league pitching is not the toughest thing to do in sport.