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