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.
Killed a Chubby
Unsheathed 5 swords from Immortal Skeletaurs without leaving the area
Introduced thyself to the White Knight
Demonstrated your skill, or lack thereof, at rolling the magical treasure orb of many sides
Slew Mister Boney Pants Guy
Opened the chest at the bus stop in Fyrestone
Reached level 50
Killed Donkey Mong
Gunzerked continuously for 90 seconds
Completed the mission "Long Way To The Top"
Completed the mission "X Marks the Spot"
Defeated Jack
Completed the mission "Data Mining"
Completed the mission "Toil And Trouble"
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"
Defeated Terramorphous the Invincible
Allowed a Goliath to level up four times before killing him
Killed 100 enemies with the Sabre turret
Reached level 25
Completed Round 5 of any Circle of Slaughter
Remained in Zero's Deception mode for ten seconds straight
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
Gave Claptrap a high five
Phaselocked 100 enemies
Completed the mission "Wildlife Preservation"
Tipped Moxxi $10,000
Completed the mission "Bright Lights, Flying City"
Completed the mission "Rising Action"
Completed the mission "A Train To Catch"
Killed a flying enemy with a thrown Tediore weapon
Killed a Constructor without it ever building another bot
Purchased 5 items from the black market
Completed 20 side missions
Completed the mission "A Dam Fine Rescue"
Unlocked 10 customization items
Redeemed 25 tokens
Completed the mission "Hunting The Firehawk"
Reached level 10
Completed the mission "Plan B"
Got an item from Michael Mamaril
Completed the mission "The Road To Sanctuary"
Completed the mission "Best Minion Ever"
Reached level 5
Revived someone from "Fight for Your Life!" that is on your friends list
Completed the mission "My First Gun"
Complete level 1 of all non-level-specific challenges with a single character
Have Purple-rated gear or better equipped in every slot
Hidden
Complete all side missions
Discover all named locations in Oasis and the surrounding Pirate's Booty zones
Complete all Pirate's Booty side missions
Complete all Campaign of Carnage side missions
Collect 10 pictures of Moxxi in Campaign of Carnage
Complete the mission "The Fall of Nakayama"
Complete all Hammerlock's Hunt side missions
Discover all named locations in Hammerlock's Hunt
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
Win the most challenging round in Murderlin's Temple
Wield the Mysterious Amulet
Vanquish the Ancient Dragons of Destruction
Completed the mission "Paradise Found".
Defeated the Dark Web.
Allowed Tiny Tina to arm the moonshot cannon.
Activated the Backburner's firewall.
Defeat Haderax the Invincible.
Equip effervescent-quality gear in all slots (except class mod).