Here is the full list of all 22 Flynn: Son of Crimson achievements.
Completed all levels, acquired every relic and learned every skill.
Complete the 6 challenge stages.
Defeat a training dummy in Sanctia.
Acquire every skill from Loretta.
Using the sword, pogo-bounce on 4 separate enemies without touching the ground.
Find Bax in 4 separate locations.
Quickly skip Bohrin's dialogue.
Have a throwable rock bounce on an enemy 5 consecutive times without touching the ground.
Find, collect and sell all 20 relics to Yombal.
Have an enemy frozen, burned and zapped simultaneously.
Perform a full plummet combo with any Crimson weapon.
Starting with an uppercut, perform a full aerial combo with any Crimson weapon.
Defeat Zealock
Defeat Imbra the Shadow Sorceress.
Defeat Xellios the Toxic Marksman.
Defeat Rozia for the final time in the Desolate Woods.
Chain zap 7 enemies with lightning magic.
Defeat Kravios the Aquatic Voltknight.
Defeat Bora the Whirlwind Assassin.
Acquired your first skill.
Find and collect a golden relic.
Set out on an adventure with your beloved friend, Dex.