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