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