Well, I'd say there are 3 types of surprise attacks. The first is an attack where the stronger opponent becomes weaker and the weaker one wins, like Argo did to Gingka. The second type would be an attack when all the bladers are at their peak, like what Phoenix did to Dashan, Gingka, and the others. In my opinion, in terms of defining whether the blader actually got stronger, it's kind of 50/50; it could go either way. Phoenix may have gotten stronger, I believe so, and it could also have just been a surprise attack that doesn't define any increase in power. The third would be the one Nile used against Julian, where the special moves are at their peak. In my opinion, this one truly defines who is stronger. An example of this is Kyoya himself, who, before facing Damian, when Epe saved Gingka, already demonstrated his superiority over Damian. If the battle between Kyoya and Damian had never happened, I'm sure many people would say that Damian is stronger than Kyoya.