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