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.
Discovered Sledge's Safe House
Earned level 50
Earned level 40
Completed 15 missions in co-op
Killed 15 enemies with the Hunter's action skill
Killed 25 enemies by ramming them with any vehicle
Killed 15 enemies with the Soldier's action skill
Killed the Vault Boss
Discovered Eridian Promontory
Completed all missions in the Rust Commons
Rescued enough Claptraps to earn 42 inventory slots
Discovered Crimson Lance Enclave
Killed Flynt
Earned $1,000,000
Raced around the Ludicrous Speedway in record time
Earned level 30
Killed the Rakk Hive
Discovered Trash Coast
Killed an enemy with the Siren's action skill
Emerged victorious from an arena match
Killed Krom
Sold 50 guns to a shop
Completed all missions in the Arid Badlands
Killed an enemy plumber-style
I bet you never thought you'd be here.
Discovered Krom's Canyon
Completed 5 missions in the Rust Commons
Discovered The Scrapyard
Reached proficiency level 10 with any weapon type
Killed 25 enemies with corrosive weapons
Rescued a groupmate from death in a co-op game
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
Discovered Headstone Mine
Won a duel against another player
Won a duel without taking damage
Killed 25 enemies with incendiary weapons
Gamed with fame
Killed 25 enemies with shock weapons
Mastered the technology of Pandora
Applied an elemental artifact
Killed 5 Rakk in under 10 seconds
Killed 25 enemies with explosive weapons
Earned level 10
Killed 15 enemies with the Berserker's action skill
Discovered Skag Gully
Earned level 5
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
Complete 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
Killed each of the loot midgets
Destroyed the Lance Depot
Rescued Athena
Destroyed a Lancer while in a Racer
Built the New Car: Monster
Kill Crawmerax the Invincible
Complete all missions in Secret Armory
Pay for a worthless tour of the world's largest bullet
Reached Level 51
Read all 6 Claptrap statue placards
Completed Tannis' crazy request
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