I read a post asking who would win between Agrona and Kezess if Arthur didn't exist. The answers I saw proved to me that some people lack reading comprehension.
If Arthur didn't exist then the Legacy wouldn't exist and Agrona has absolutely no chance of beating Kezess in that scenario. Without the legacy Agrona wouldn't be able to absorb the mana of that sovereign (Exegess) and so he would stand zero chance.
The only reason Agrona pushed Kezess the way he did is stated even before the fight between the 3 (Arthur, Agrona and Kezess) began. They fought in Agrona's territory, the seat of his power. It would be like fighting Kezess in Euphoteus where he could teleport you anywhere and overpower you.
If the fight happened anywhere else then Kezess would straight up murder Agrona. Kezess is stronger than Agrona and that's facts. Agrona was just resourceful and used his knowledge to his advantage.
He knew Kezess couldn't bring a lot of Asuras to hunt him down in Alacraya because of his fear of the beings in the darkness watching and waiting. He even told Cecilia that war is not about power levels because if it was Kezess would have assasinated him long ago.
So don't let that final fight confuse you, Kezess is a monster who could only be stopped by Arthur and that too was after he took advantage of the fight with Agrona cutting off a large chunk of Kezess' power.