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