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