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