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