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