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