I don't know if anyone said this already BUT if you Forcetame the deathworm on single player or something, it eats meat! In order for the death worm to get out from the ground, you need to first, locate where it's at then step either on or around the worm and it'll come out.
Tame a 100+ megatherium and enrage is by attacking creatures that give you chitin. This will give you a damage boost and a damage resistance boost. Level up melee and you will easily be able to kill a death worm