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