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