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