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