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 all side missions
Completed all Hammerlock's Hunt side missions
Discovered all named locations in Hammerlock's Hunt
Completed the mission "The Fall of Nakayama"
Completed all Pirate's Booty side missions
Discovered all named locations in Oasis and the surrounding Pirate's Booty zones
Completed the mission "X Marks the Spot"
Demonstrated your skill, or lack thereof, at rolling the magical treasure orb of many sides
Vanquished the Ancient Dragons of Destruction
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
Completed the mission "Long Way To The Top"
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"
I can't even capture it on my camera
Completed the mission "Shoot This Guy in the Face"
Won the most challenging round in Murderlin's Temple
Completed all Campaign of Carnage side missions
Completed Round 5 of any Circle of Slaughter
Got an item from Michael Mamaril
Allowed a Goliath to level up four times before killing him
Tipped Moxxi $10,000
Remained in Zero's Deception mode for ten seconds straight
Gunzerked continuously for 90 seconds
Reached level 5
Reached level 10
Reached level 25
Reached level 50
Killed a flying enemy with a thrown Tediore weapon
Killed Donkey Mong
Killed a Chubby
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"
Gave Claptrap a high five
Completed the mission "Wildlife Preservation"
Completed the mission "Bright Lights, Flying City"
Killed a Constructor without it ever building another bot
Completed the mission "Rising Action"
Completed the mission "A Train To Catch"
Completed the mission "A Dam Fine Rescue"
Completed the mission "Hunting The Firehawk"
Completed the mission "Plan B"
Purchased 5 items from the black market
Completed the mission "My First Gun"
Collected 10 pictures of Moxxi in Campaign of Carnage
Completed the mission "The Road To Sanctuary"
Unlocked 10 customization items
Completed the mission "Best Minion Ever"
Revived someone from "Fight for Your Life!" that is on your friends list
Completed 20 side missions
Redeemed 25 tokens
Had Purple-rated gear or better equipped in every slot
Wielded the Mysterious Amulet
Completed level 1 of all non-level-specific challenges with a single character
Discovered all named locations in Three Horns, Tundra Express, and Frostburn Canyon
Discovered all named locations in Sanctuary, Opportunity, and Lynchwood
Discovered all named locations in The Highlands, Thousand Cuts, and Wildlife Exploitation Preserve
Discovered all named locations in Eridium Blight, Arid Nexus, and Sawtooth Cauldron
Discovered all named locations
Killed 100 enemies with the Sabre turret
Phaselocked 100 enemies
Equipped effervescent-quality gear in all slots (except class mod).
Defeated Haderax the Invincible.
Defeated the Dark Web.
Activated the Backburner's firewall.
Allowed Tiny Tina to arm the moonshot cannon.
Completed the mission "Paradise Found".