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