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