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