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