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