Here is the full list of all 70 Gryphon Knight Epic achievements.
Defeat one boss with his own weapon
Defeat Asterion Hornedson
Defeat Lorraine Learn
Defeat the Kraken
Defeat the Djur War Elephant
Get all the rare potion drops
Defeat Eugenia Frischengust
Defeat the Frogmoth
Defeat 300 enemies with the Dragon Squire
Reach a 50 combo
Defeat Dawid Melekh
Defeat the Giant
Defeat 300 enemies with the Muuk Bow
Upgrade one weapon or rune to the maximum
Defeat Zafira Faris
Defeat the Ifrit
Defeat Simiel Totec
Defeat a boss with only 1 HP left
Defeat TreeStache
Defeat 2000 enemies with the Crossbuster
Defeat 300 enemies with the Qamar Sword
Defeat 300 enemies with the Kraft Staff
Defeat 300 enemies with the Skadi Lance
Defeat 300 enemies with the Eben Sling
Defeat 300 enemies with the Ryunabbi Cannon
Defeat 20 enemies with 1 bomb
Defeat 20 enemies with one Berserk Potion
Defeat 200 enemies with the Witch Coven Squire
Use the Shield Squire protection 40 times
Absorb 100 HP using the Vampire Squire
Reach a 100 combo
Collect 5000 gold in one stage
Complete the game on Squire difficulty
Complete the game on Knight difficulty
Complete the game on Epic difficulty
Defeat the Magical Stone Dragon
Use the Fairy Squire to revive
Take no damage and kill 10 enemies while shrunk
Watch the secret ending
Find the Rune hidden in the Zafira Faris Stage
Find the Rune hidden in the Simiel Totec Stage
Find the Rune hidden in the Eugenia Frischengust Stage
Find the Rune hidden in the Asterion Hornedson Stage
Find the Rune hidden in the Dawid Melekh Stage
Find the Rune hidden in the Lorraine Learn Stage
Silence the duckling!
Buy and use every Potion
Upgrade all weapons and runes to the maximum
Defeat all bosses using only the Crossbuster
Listen to all dialog from the Wizard and the Shopkeepper
Defeat every enemy type
Find and interact with all cameos
Buy and use every Squire
Defeat the specter in the Tutorial Stage
Dash right before a shot hits you and escape
Play through the entire game without buying any upgrades or items and using only the Crossbuster (Knight or Epic Difficulty)
Beat all stages of the game in less than 2 hours
Take no damage in the K'aax Jungle (Knight or Epic Difficulty)
Take no damage in the Huh Kobold Village (Knight or Epic Difficulty)
Take no damage in the Al-Sharaf Desert (Knight or Epic Difficulty)
Take no damage in the Al-Sharaf Village (Knight or Epic Difficulty)
Take no damage at Simpeldorf Village (Knight or Epic Difficulty)
Take no damage in the Royal's Wizard Tower (Knight or Epic Difficulty)
Take no damage in the Dödlig Mountains (Knight or Epic Difficulty)
Take no damage at Asterion's Warcamp (Knight or Epic Difficulty)
Take no damage in the Midbar Savannah (Knight or Epic Difficulty)
Take no damage at Dawid's Temple (Knight or Epic Difficulty)
Take no damage at Turquoise Bay (Knight or Epic Difficulty)
Take no damage at Lorraine's Hideout (Knight or Epic Difficulty)
Take no damage in the Katharizes Ruins (Knight or Epic Difficulty)