Here is the full list of all 64 Vzerthos: The Heir of Thunder achievements.
Get the Thunder Blade
Complete the game
Complete the game without saving and dying
Complete the first act
Complete the second act
Complete the third act
Defeat the first boss - Meditaguard
Defeat the second boss - Messenger
Defeat the third boss - Baron Vakhzon
Return the power of Thunder
Get the Monk Stave
Get the Thonance's Hammer
Get the Arbalest
Get the Tri-Crossbow
Get the Necro-Mortar
Get the Necro-Bow
Get the Hell-Thrower
Get the HellFire Spitter
Get all the guns
Unlock the 'Dash' skill
Unlock the 'Lightning Nova' skill
Unlock the 'Cutting Lightning' skill
Unlock the 'Heaven Strike' skill
Unlock the 'Punishing Glance' skill
Unlock all Vzerthos's skills
Upgrade any gun at least once
Upgrade any gun to the max
Upgrade every single gun to the max
Find all the secrets in the game
Find all the secrets in the [Dungeon, lv.1]
Find all the secrets in the [Dungeon, lv.2]
Find all the secrets in the [Dungeon, lv.3]
Find all the secrets in the [Dungeons] lv.1- lv.3
Find all the secrets in Forest locations
Find all the secrets in the Catacombs
Find all the secrets in the GraveYard
Find all the secrets in Snowy locations
Find all secrets in the Vakhzon's Castle
Find all the secrets in the Castle's dungeon
Find all the secrets in the Tower
Open the demonic door
Enter the correct password and open the Tower
Read every single article in the Cyclopedia
Kill 100 enemies
Kill 1000 enemies
Collect 15,000 gold
Collect 50,000 gold
Collect 1,000,000 gold
Pick up health upgrade artefact
Pick up 5+ health upgrades
Pick up medita upgrade artefact
Pick up 5+ medita upgrades