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