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