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