Borderlands 2

In the 9th Story mission you need to go to Tundra Express to meet .

You’ll need to wake him up by having three Varkids scream by burning them.
- You can use a fire elemental weapon
- You can try to gather them up and hit a firemelon, in their first form they will run up to hit you and you can then hit the firemelon
- You can trigger the tall fire pylons to try and burn them.
Make sure you don't kill them.

Once he is awake, you must speak to Tiny Tina. Follow the map and get to her workshop.

After meeting Tiny Tina, you receive a quest update to retrieve her 'badonkadonks'. The markers on the updated map are where you need to go.

Following the train track (and avoiding the train) will lead you straight to one of the badonkadonk's and can then try to avoid most baddies while making a dash for the other. Otherwise you can fight your way through the compound to retrieve them.

Take them back to the worshop, wait a minute, then proceed to the next location. Staying in the water and going around can help you avoid the bad guys across the bridge.

Fast Travel to: The End of the Line.
Make your way through the path of the damaged loaders. Keep an eye out for repair surveyors and EXP loaders that will come running at you.

Then the battle of Wilhelm.

Keep your distance from him, watch out for the loaders, and prioritize the shield repair bots. Use corrosive if you have it and once you take him down, grab the shield core and head to Sanctuary.

This achievement is story based and should be completed during natural progression. A Train to Catch is a main mission that chronologically occurs as below:

My First Gun
Blindsided
Cleaning Up the Berg
Best Minion Ever
The Road to Sanctuary
Plan B
Hunting the Firehawk
A Dam Fine Rescue
A Train to Catch

Essentially, after turning in A Dam Fine Rescue to Roland, this will begin A Train to Catch. Use the nearby fast travel to go back to Sanctuary and speak with Roland again who informs you Handsome Jack isn't trying to open a Vault, he wants to control one. In order to take control of it yourself, you'll need to get the Vault Key from Jack. Roland's spy out in the Tundra Express should know the location of the Key.

Before leaving, make sure you have a fire based weapon or purchase one from Marcus. When you're ready, fast travel to Three Horns - Divide and Catch-a-Ride on your left. Head NW and pop off your ride to enter the fence and entrance to Tundra Express.

Your first goal is to ignite 3 varkids with the fire weapon mentioned earlier. Go N to Varkid Ranch Observatory and shoot enough varkids in a short period of time so several of them are on fire at once. This will trigger a cutscene introducing Mordecai and his BFF Bloodwing.

Mordecai tells you the key will be located aboard the train and Roland suggests you speak to Tiny Tina to find a way to hijack it. Tina is located in her Workshop just to the N but you will have to go to the left or right of the mountain in front of you go get there. Once inside, another cutscene begins to introduce the engineer to you.

Speak with Tina then follow her into the garage where the dynamite bunnies appear to be missing their "badonkadonks" and you have to go fetch them. Leave the Workshop and travel SW to the Buzzard Academy where you fight through a horde of bandits to pick up the two missiles. Now bring them back to Tina and she'll prepare the bombs in her garage.

Pick up your cute weapons of destruction and head E to Meltwater Crossing. Fight through more bandits then climb the ladder up to the platform to setup the bombs facing the train track. Then arm each rocket and the train will sound its approach before one bomb blows up the track and the other hits the actual train. Climb up the destroyed track to enter the area End of the Line.

Stock up to the left before making your way through the one path in this zone. Continue fighting Loader Bots along the way until you reach a clearing where you'll find the fortified train car. Wilhelm will rise from under a train car and engage you in battle. Once he's been dealt with, grab the power core he drops and backtrack to the fast travel. Head back to Sanctuary and turn in the quest to Lt. Davis in the SW outside the gate.

The achievement should pop and you'll be rewarded with:
- Approx $39
- Approx 2730 XP
- Elemental Relic (White)