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