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