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