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