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