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.
All achievements
Achievements they've won
Achievements they've not won
Killed Flynt
Kill 5 Rakk in under 10 seconds
Earn $1,000,000
Race around the Ludicrous Speedway in under 31 seconds
Kill 25 enemies with shock weapons
Earn level 30
Killed the Rakk Hive
Discover Trash Coast
Kill 25 enemies with corrosive weapons
Reach proficiency level 10 with any weapon type
Killed Krom
Discover Krom's Canyon
I bet you never thought you'd be here.
Complete 5 missions in the Rust Commons
Discover The Scrapyard
Kill 15 enemies with the Hunter's action skill
Kill 25 enemies with explosive weapons
Kill 25 enemies by ramming them with any vehicle
Defeat the Rakk Hive, the Vault Boss, Sledge, Krom, or Flynt in a co-op game
Earn level 20
Master the technology of Pandora
Equip a class mod for your character
Killed Sledge
Sell 50 guns to a shop
Discover Headstone Mine
Win a duel against another player
Win a duel without taking damage
Apply an elemental artifact
Kill 25 enemies with incendiary weapons
Discover Sledge's Safe House
Earn level 10
Rescue a groupmate from death in a co-op game
Complete 15 missions in co-op
Kill an enemy by stomping on its head
Complete 5 missions in the Arid Badlands
Earn level 5
Discover Skag Gully
Play in a co-op game with either an employee of Gearbox or someone who has this achievement
Complete all missions in the Arid Badlands
Complete all missions in the Rust Commons
Killed the Vault Boss
Earn level 40
Discover Crimson Lance Enclave
Discover Eridian Promontory
Earn level 50
Win an arena match
Rescue enough Claptraps to earn 42 inventory slots
Kill an enemy with the Siren's action skill
Kill 15 enemies with the Berserker's action skill
Kill 15 enemies with the Soldier's action skill
Complete 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
Build the New Car: Monster
Rescue Athena
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
Find all 6 Claptrap Statues
Kill General Knoxx-Trap
Kill Commandant Steele-Trap
Kill Dr. Ned-Trap
Kill the INAC
Complete a crazy request for Tannis
Find 25 oil cans
Collect 15 claptrap bobbleheads
Collect 5 3D glasses
Collect 3 panties, 5 fish in a bag, and 15 pizzas