Full list of all 69 Borderlands 2 achievements worth 1,625 gamerscore. It takes around 40-50 hours to unlock all of the achievements in the base game.
The base game contains 50 achievements worth 1,000 Gamerscore, and there are 4 DLC packs containing 19 achievements worth 625 Gamerscore.
Gunzerked continuously for 90 seconds
Completed level 1 of all non-level-specific challenges with a single character
Killed a Chubby
Completed all side missions
Had Purple-rated gear or better equipped in every slot
Reached level 50
Defeated Terramorphous the Invincible
Phaselocked 100 enemies
Discovered all named locations in Three Horns, Tundra Express, and Frostburn Canyon
Killed 100 enemies with the Sabre turret
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
Revived someone from "Fight for Your Life!" that is on your friends list
Completed Round 5 of any Circle of Slaughter
Defeated Jack
Remained in Zero's Deception mode for ten seconds straight
Completed the mission "Data Mining"
Opened the chest at the bus stop in Fyrestone
Completed the mission "Toil And Trouble"
Allowed a Goliath to level up four times before killing him
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
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
Killed a Constructor without it ever building another bot
Completed the mission "Bright Lights, Flying City"
Completed the mission "Rising Action"
Completed the mission "A Train To Catch"
Completed 20 side missions
Tipped Moxxi $10,000
Purchased 5 items from the black market
Completed the mission "A Dam Fine Rescue"
Redeemed 25 tokens
Completed the mission "Hunting The Firehawk"
Reached level 10
Got an item from Michael Mamaril
Completed the mission "Plan B"
Completed the mission "The Road To Sanctuary"
Killed a flying enemy with a thrown Tediore weapon
Completed the mission "Best Minion Ever"
Reached level 5
Unlocked 10 customization items
Completed the mission "My First Gun"
Discovered all named locations in Oasis and the surrounding Pirate's Booty zones
Completed all Pirate's Booty side missions
Completed the mission "X Marks the Spot"
Completed all Campaign of Carnage side missions
Completed the mission "Long Way To The Top"
Collect 10 pictures of Moxxi in Campaign of Carnage
Discovered all named locations in Hammerlock's Hunt
Completed the mission "The Fall of Nakayama"
Complete all Hammerlock's Hunt side missions
Slay Mister Boney Pants Guy
Introduce thyself to the White Knight
Complete thy quest by rescuing yonder queen
Feed thy noble queen 3 times during one visit to her quarters
Show thine worst enemy, the abomination known as "The Darkness," who is the nerdiest of them all
Unsheath 5 swords from Immortal Skeletaurs without leaving the area
Win the most challenging round in Murderlin's Temple
Wield the Mysterious Amulet
Demonstrate your skill, or lack thereof, at rolling the magical treasure orb of many sides
Vanquish the Ancient Dragons of Destruction