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