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