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