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