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