Radiance with detonate antimatter. Kind of silly to compare a capital ship killer with two anti-strike craft capital ships in direct combat. As I've said before, the Kol and Kortul are comparable, but the Radiance fulfills an entirely different purpose. It's like comparing the Skirantra and the Sova; their both carriers but this is all they share in common!
edit: actually since you specifically designate a FFA scenario, I'm not sure. Certainly if this were separate 1v1 comparisons, I'd go with Radiance, but a FFA would result in a longer more drawn out battle that would certainly favour Kortul. Kol remains the toughest and also benefits from this, but its abilities will get neutralized.
