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