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