The revenge was satisfactory and pretty entertaining. Some plot elements are kinda meeh, but it doesn't really make a huge difference in the general overall story.  The FL doesn't do anything remarkable and her descent into "evil" also makes her blend into the background and she ends up not really doing much in her story. You feel bad for her in what has been done to her, but the sympathy doesn't help how milktoast bland she is. The real star is Ragna, the evil dragon... and he is as Evil as can be, inflicting revenge on those who have wronged him and his bride in previous lives.