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