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