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