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