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