Here is the full list of all 119 Torchlight II achievements. It takes around 200 hours to unlock all of the achievements on Windows.
Sell 50,000 items
Use 5,000 potions
Have 50 friends
Deal 100,000 critical strikes
Reach level 100
Obtain a tier 3 skill bonus
Defeat the Nether King with each of the 4 classes
Defeat the Nether King as an Engineer
Defeat the Nether King in hardcore mode (elite)
Defeat the Nether King in hardcore mode (veteran)
Break 10,000 breakables
Find a legendary item
Purchase 100 items from the gambler
Purchase 50 items from the gambler
Use an enchanter 500 times
Have 10,000,000 gold
Sell 5,000 items
Use 100 maps
Use 10 maps
Have 1,000,000 gold
Find 100 secret rooms
Squish 1000 critters
Destroy 100 socketed gems
Socket 500 gems into items
Defeat 500 champions
Fish 1,000 times
Deal 10,000 critical strikes
Defeat the Nether King in hardcore mode (casual)
Defeat the Nether King in hardcore mode (normal)
Defeat the Nether King as an Outlander
Do 10,000 damage with a single attack
Begin new game plus
Defeat the Nether King in Elite difficulty
Defeat the Nether King in Normal difficulty
Defeat the Nether King in Veteran difficulty
Defeat the Nether King as an Embermage
Defeat Aleera
Defeat Verona
Defeat Marishka
Assemble TrillBot
Find 10 secret rooms
Defeat Boletus Rex
Have 100,000 gold
Take 100,000 steps
Recover 100 gems from items
Explode 10,000 enemies
Squish 500 critters
Use 500 potions
Socket 50 gems into items
Recover 10 gems from items
Destroy 10 socketed gems
Use an enchanter 50 times
Defeat One-Eyed Willy
Fish using dynamite
Have 10 friends
Trade an item with another player
Die with a hardcore character
Join a multiplayer game
Add a friend
Start a hardcore character
Start a multiplayer game
Use a map
Defeat the Nether King as a Berserker
Defeat the Nether King in Casual difficulty
Defeat the Nether King
Defeat the Dark Alchemist
Teach a pet 4 spells
Teach a pet a spell
Learn 4 spells
Defeat Killbot
Defeat Vyrax
Recover a gem from an item
Purchase 20 items from the gambler
Destroy a socketed gem
Defeat Thiss
Defeat Cacklespit
Fish 100 times
Take 50,000 steps
Defeat Bloatfang
Defeat the Grizzled Alpha
Defeat the Wraith Lord
Obtain a tier 2 skill bonus
Defeat the Siege Guardian
Break 1,000 breakables
Defeat Ezrek Khan
Defeat Aruk
Open 500 chests
Use 50 potions
Defeat the King In Masks
Defeat 100 champions
Deal 1,000 critical strikes
Defeat the Artificer
Squish 100 critters
Sell 500 items
Use an enchanter 10 times
Defeat the Manticore's Mate
Defeat the Manticore
Defeat Grand Regent Eldrayn
Defeat King Pogg
Wear a completed armor set
Defeat Kidrik the Mauler
Defeat Chillhoof
Take 10,000 steps
Defeat the Winter Widow
Defeat 25 champions
Explode 1,000 enemies
Defeat General Grell
Obtain a tier 1 skill bonus
Find a secret room
Open 100 chests
Learn a spell
Defeat Mordrox
Break 100 breakables
Fish 10 times
Defeat the Fallen Guardian
Send your pet to town
Open 20 chests
Explode 100 enemies
Socket a gem into an item