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