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