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