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