Use 3 metal dino gateway and a large bear trap. Once inside, close with a 4th gateway. Kill a baby diplo or bronto and offer the sacrifice, may take 2 sacrifices but be ready. Once over the creature and out of the trap, try to kill large creatures like diplo, after every kill it gains damage immunity for a few seconds but try to not expose the dino to attacks and you maybe tame it with 100% effectiveness.