Honestly the turning point of this manga for me was the war in the magician country. The field battle with the Queen posing in front of her army was just too good, and the development after that was overall amazing.
But this new arc is reaching new heights in character development. I wish more people were reading it. Usually I'm very unconvinced by manga written by french authors (they mostly feels too localized while still staying in the manga genre. I'd rather read full fledged Bande Dessinées or full fledged manga, not something in between), but Radiant has been nothing but good surprise.