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