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