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