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