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