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