If you want to remove your current game character, you can do it by clicking on [Avatar]-[Settings]-[Delete Character] at the top left corner in the game.
If you want to remove your full game account, you can do this by clicking on [Avatar]-[Settings]-[General Settings]-[Delete Account] at the top left corner in the game. This will delete your game account, including all the characters associated with it.
Please note: Once the account/character is deleted, it can't be restored. Please think it over carefully!
We hope this can help you clear your doubts, thank you for reaching out, We hope you enjoy the game.