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