Full list of all 80 Borderlands achievements. It takes around 50-60 hours to unlock all of the achievements in the base game on Windows.
The base game contains 50 achievements, and there are 4 DLC packs containing 30 achievements.
Defeated the Rakk Hive, the Vault Boss, Sledge, Krom, or Flynt in a co-op game
Completed 15 missions in co-op
Killed an enemy with the Siren's action skill
Killed an enemy plumber-style
Earned level 50
Earned level 40
Killed the Vault Boss
Discovered Eridian Promontory
Discovered Crimson Lance Enclave
Completed all missions in the Rust Commons
Killed Flynt
Rescued enough Claptraps to earn 42 inventory slots
Killed 15 enemies with the Soldier's action skill
Killed the Rakk Hive
Discovered Trash Coast
Earned $1,000,000
Earned level 30
Killed Krom
Discovered Krom's Canyon
I bet you never thought you'd be here.
Reached proficiency level 10 with any weapon type
Killed 25 enemies with shock weapons
Discovered The Scrapyard
Completed 5 missions in the Rust Commons
Killed 25 enemies with corrosive weapons
Raced around the Ludicrous Speedway in record time
Mastered the technology of Pandora
Completed all missions in the Arid Badlands
Equipped a class mod for your character
Killed 25 enemies by ramming them with any vehicle
Earned level 20
Killed Sledge
Discovered Headstone Mine
Applied an elemental artifact
Sold 50 guns to a shop
Discovered Sledge's Safe House
Killed 5 Rakk in under 10 seconds
Killed 25 enemies with explosive weapons
Earned level 10
Killed 25 enemies with incendiary weapons
Discovered Skag Gully
Earned level 5
Completed 5 missions in the Arid Badlands
Emerged victorious from an arena match
Won a duel against another player
Rescued a groupmate from death in a co-op game
Gamed with fame
Won a duel without taking damage
Killed 15 enemies with the Hunter's action skill
Killed 15 enemies with the Berserker's action skill
Killed Ned. Again.
Killed Ned...sort of
Completed the "Braaaaaaaaaaaaains!" mission
Completed the "Jakobs Fodder" mission
Completed the "House of the Ned" mission
Completed the Prove Yourself mission
Reached the end of the larger challenge in the Hell-Burbia coliseum
Reached the end of the larger challenge in The Angelic Ruins coliseum
Reached the end of the larger challenge in The Gully coliseum
Reached the end of each of the 3 larger challenges with one character
Reached Level 61
Reached Level 51
Destroyed the Lance Depot
Killed each of the loot midgets
Rescued Athena
Destroyed a Lancer while in a Racer
Built the New Car: Monster
Killed Crawmerax the Invincible
Completed all missions in Secret Armory
Paid for a worthless tour of the world's largest bullet
Read all 6 claptrap statue placards
Defeated the Interplanetary Ninja Assassin Claptrap
The Commandant is dead-trap
Killed Ned... again and again and again
Knoxx is at rest...finally
Completed Tannis' crazy request
Collected 5 3D glasses
Found 25 claptrap oil cans
Collected 15 claptrap bobbleheads
Collected 3 panties, 5 fish in a bag, and 15 pizzas