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