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