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