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