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