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