Full list of all 75 Borderlands 2 achievements worth 1,875 gamerscore. It takes around 60-80 hours to unlock all of the achievements in the base game.
The base game contains 69 achievements worth 1,625 Gamerscore, and there is 1 DLC pack containing 6 achievements worth 250 Gamerscore.
Completed level 1 of all non-level-specific challenges with a single character
Reached level 50
Collected 10 pictures of Moxxi in Campaign of Carnage
Demonstrated your skill, or lack thereof, at rolling the magical treasure orb of many sides
Vanquished the Ancient Dragons of Destruction
Completed all Campaign of Carnage side missions
Completed all Hammerlock's Hunt side missions
Won the most challenging round in Murderlin's Temple
Had Purple-rated gear or better equipped in every slot
Phaselocked 100 enemies
Gunzerked continuously for 90 seconds
Killed 100 enemies with the Sabre turret
Discovered all named locations in Oasis and the surrounding Pirate's Booty zones
Discovered all named locations in Eridium Blight, Arid Nexus, and Sawtooth Cauldron
Discovered all named locations
Completed all side missions
Remained in Zero's Deception mode for ten seconds straight
Discovered all named locations in The Highlands, Thousand Cuts, and Wildlife Exploitation Preserve
Completed all Pirate's Booty side missions
Showed thine worst enemy, the abomination known as "The Darkness," who is the nerdiest of them all
Fed thy noble queen 3 times during one visit to her quarters
Completed thy quest by rescuing yonder queen
Unsheathed 5 swords from Immortal Skeletaurs without leaving the area
Introduced thyself to the White Knight
Slew Mister Boney Pants Guy
Discovered all named locations in Hammerlock's Hunt
Killed a flying enemy with a thrown Tediore weapon
Completed the mission "The Fall of Nakayama"
Discovered all named locations in Sanctuary, Opportunity, and Lynchwood
Wielded the Mysterious Amulet
Killed Donkey Mong
Completed the mission "X Marks the Spot"
Defeated Terramorphous the Invincible
Defeated Jack
Completed the mission "Data Mining"
Opened the chest at the bus stop in Fyrestone
Completed the mission "Toil And Trouble"
Gave Claptrap a high five
Completed the mission "Where Angels Fear To Tread"
Completed the mission "The Man Who Would Be Jack"
Completed the mission "The Once and Future Slab"
Completed the mission "Shoot This Guy in the Face"
Completed the mission "Long Way To The Top"
Completed the mission "Wildlife Preservation"
Reached level 25
Purchased 5 items from the black market
Completed the mission "Bright Lights, Flying City"
I can't even capture it on my camera
Completed Round 5 of any Circle of Slaughter
Redeemed 25 tokens
Unlocked 10 customization items
Completed the mission "Rising Action"
Discovered all named locations in Three Horns, Tundra Express, and Frostburn Canyon
Completed the mission "A Train To Catch"
Killed a Chubby
Allowed a Goliath to level up four times before killing him
Got an item from Michael Mamaril
Completed 20 side missions
Killed a Constructor without it ever building another bot
Tipped Moxxi $10,000
Completed the mission "A Dam Fine Rescue"
Completed the mission "Hunting The Firehawk"
Reached level 10
Completed the mission "Plan B"
Completed the mission "The Road To Sanctuary"
Completed the mission "Best Minion Ever"
Revived someone from "Fight for Your Life!" that is on your friends list
Reached level 5
Completed the mission "My First Gun"
Defeated Haderax the Invincible.
Equipped effervescent-quality gear in all slots (except class mod).
Completed the mission "Paradise Found".
Defeated the Dark Web.
Allowed Tiny Tina to arm the moonshot cannon.
Activated the Backburner's firewall.