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