Full list of all 80 Borderlands achievements worth 1,750 gamerscore. It takes around 40-50 hours to unlock all of the achievements in the base game on Xbox 360.
The base game contains 50 achievements worth 1,000 Gamerscore, and there are 5 DLC packs containing 30 achievements worth 750 Gamerscore.
Killed an enemy with the Siren's action skill
Earned level 50
Earned level 40
Completed all missions in the Rust Commons
Killed 15 enemies with the Berserker's action skill
Emerged victorious from an arena match
Rescued enough Claptraps to earn 42 inventory slots
Raced around the Ludicrous Speedway in record time
Killed the Rakk Hive
Discovered Trash Coast
Discovered Crimson Lance Enclave
Killed Flynt
Killed Krom
Earned level 30
Killed the Vault Boss
Mastered the technology of Pandora
I bet you never thought you'd be here.
Earned $1,000,000
Discovered Krom's Canyon
Killed 25 enemies with corrosive weapons
Completed all missions in the Arid Badlands
Discovered Eridian Promontory
Killed 5 Rakk in under 10 seconds
Killed 15 enemies with the Soldier's action skill
Discovered The Scrapyard
Killed 25 enemies with shock weapons
Reached proficiency level 10 with any weapon type
Completed 5 missions in the Rust Commons
Killed 15 enemies with the Hunter's action skill
Earned level 20
Equipped a class mod for your character
Defeated the Rakk Hive, the Vault Boss, Sledge, Krom, or Flynt in a co-op game
Killed Sledge
Killed 25 enemies with incendiary weapons
Won a duel against another player
Won a duel without taking damage
Discovered Headstone Mine
Applied an elemental artifact
Discovered Sledge's Safe House
Killed an enemy plumber-style
Sold 50 guns to a shop
Killed 25 enemies with explosive weapons
Killed 25 enemies by ramming them with any vehicle
Earned level 10
Completed 15 missions in co-op
Discovered Skag Gully
Rescued a groupmate from death in a co-op game
Earned level 5
Completed 5 missions in the Arid Badlands
Gamed with fame
Killed Ned...sort of
Killed Ned. Again.
Completed the "Braaaaaaaaaaaaains!" mission
Completed the "Jakobs Fodder" mission
Completed the "House of the Ned" mission
Reached the end of the larger challenge in the Hell-Burbia coliseum
Reached the end of each of the 3 larger challenges with one character
Reached the end of the larger challenge in The Gully coliseum
Reached the end of the larger challenge in The Angelic Ruins coliseum
Completed the Prove Yourself mission
Completed all missions in Secret Armory
Destroyed the Lance Depot
Paid for a worthless tour of the world's largest bullet
Destroyed a Lancer while in a Racer
Killed each of the loot midgets
Rescued Athena
Reached Level 61
Killed Crawmerax the Invincible
Built the New Car: Monster
Reached Level 51
Collected 15 Claptrap bobbleheads
Found 25 Claptrap oil cans
Collected 3 panties, 5 fish in a bag, and 15 pizzas
Completed Tannis' crazy request
Collected 5 3D glasses
Read all 6 Claptrap statue placards
Defeated the Interplanetary Ninja Assassin Claptrap
The Commandant is dead-trap
Killed Ned...again and again and again
Knoxx is at rest...finally