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