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