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