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