Gather as much thermal energy as possible before you fight the worm. To get more thermal energy, destroy the surrounding heat tankards and activate the outpost. If you need more thermal energy, just kill the surrounding flying Akrid and their spawn points. Get a sled VS and attach either a rocket launcher or gatling gun (recommended). Ride it just to the entrance of the Snow Plain. If you ride it any further the worm will knock you off and destroy the VS. Once you get off the sled VS, take off the weapon you brought with you. The gatling gun is recommended because if you miss you can adjust your aim and keep shooting him unlike the rocket launcher. Wait until he emerges from the snow and be ready for him to either growl or charge at you. If he charges and hits you, you are dead. You can either roll to the left or right. After the roll aim at his sides and you will see several weak points. Shoot at them until they explode and reveal a reddish boil. Continue to do this until they are all gone then switch sides. Once he is hurt enough he may start shooting flaming balls that explode from his backside. Be ready to evade them. Once again you will see more weak points. Do the same thing as done with his head side and he will eventually die. When he dies he will leave behind a large deposit of thermal energy. The worm will re-appear no matter how many times you kill it. Also the achievement for killing it will not appear until you complete the level.