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