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