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