Tramm Ride Achievement
Defeat the Tentacle Beast of Tramm. "One-two shot right to the tentacles."
This is a story related achievement, which will unlock with natural progression.
This boss is by far one of the most frustrating parts of Eat Lead. There are three different attack waves, which you need to complete to destroy the sea monster. The tentacles are rather unpredictable, so keep on the move at all times and watching for when a tentacle makes a large splash.
There are checkpoints between each wave of attacks; you will also be facing soldiers as well. Rather than dealing with them directly the sea monster will normally kill them for you when it slams into the ships deck. Try to concentrate more on the monster than the other distractions.