For kill one of these i use a good Sword with 400% damage and a wooden Shield with 4000 of durabilité because the wooden Shield can be repaired anytime and anywhere but watch out when he hors out if the grownd use the shield
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
Only fall victim to torpor from cannons and such, bring loads of narcotics because it drops real fast, once it is unconscious it must be fed wyvern milk, it takes a lot so bring all the milk you have/can get. All are level one and take 12 milk.