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