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