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