Here is the full list of all 22 Flynn: Son of Crimson achievements.
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.
Have an enemy frozen, burned and zapped simultaneously.
Completed all levels, acquired every relic and learned every skill.
Acquire every skill from Loretta.
Find, collect and sell all 20 relics to Yombal.
Complete the 6 challenge stages.
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 a training dummy in Sanctia.
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.