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