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