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 5 missions in the Arid Badlands
Earned level 5
Discovered Skag Gully
Earned level 50
Killed an enemy with the Siren's action skill
Rescued a groupmate from death in a co-op game
Won a duel against another player
Won a duel without taking damage
Emerged victorious from an arena match
Rescued enough Claptraps to earn 42 inventory slots
Completed all missions in the Rust Commons
Earned level 40
Gamed with fame
Killed the Vault Boss
Discovered Eridian Promontory
Discovered Crimson Lance Enclave
Killed Flynt
Killed the Rakk Hive
Discovered Trash Coast
Reached proficiency level 10 with any weapon type
Earned level 30
Earned $1,000,000
Killed Krom
Discovered Krom's Canyon
I bet you never thought you'd be here.
Killed 25 enemies with corrosive weapons
Discovered The Scrapyard
Completed 5 missions in the Rust Commons
Completed all missions in the Arid Badlands
Earned level 20
Equipped a class mod for your character
Killed Sledge
Discovered Headstone Mine
Applied an elemental artifact
Killed 25 enemies with shock weapons
Sold 50 guns to a shop
Discovered Sledge's Safe House
Mastered the technology of Pandora
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 15 enemies with the Soldier's action skill
Kill an enemy by stomping on its head
Race around the Ludicrous Speedway in under 31 seconds
Complete 15 missions in co-op
Defeat the Rakk Hive, the Vault Boss, Sledge, Krom, or Flynt in a co-op game
Kill 15 enemies with the Hunter's action skill
Kill 15 enemies with the Berserker's action skill
Completed the "House of the Ned" mission
Complete the "Jakobs Fodder" mission
Kill Ned
Actually kill Ned
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
Destroyed the Lance Depot
Reached Level 61
Destroyed a Lancer while in a Racer
Rescued Athena
Built the New Car: Monster
Kill Crawmerax the Invincible
Kill each of the loot midgets
Complete all missions in Secret Armory
Pay for a worthless tour of the world's largest bullet
Reached Level 51
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 all 6 Claptrap Statues
Find 25 oil cans
Collect 15 claptrap bobbleheads
Collect 3 panties, 5 fish in a bag, and 15 pizzas