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