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