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