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