In the third season of the anime when fighting against 2 saints and the knight leader, the second princess says that it's hard to fight against 3 people with saint level. The 3rd person fighting was the knight leader, who also formerly defeated a saint.
Why does the knight leader have the power level of a saint, if he isnt a saint?
This is explained in episode 12. From the Crunchyroll EngSub (the best source I could find), around the 10 minute mark, while Knight Leader is defeating Kanzaki:
Within our realm, the king is the archangel and knights are angels! I don't car if you are a saint, as long as we are in this land, the amount of power I have is on an entirely different level.
He traces this back to how the country was formed, and it is later explained that the UK itself was created by Henry VIII like this in order to be independent from the pope, so the power of the knights seems to be part of the country's structure, so Carissa was unable to take this power away from him.
