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