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