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