Kidd most likely.
For Killer it is indeed a win already being there with the others.
Law has already shown he is inferior to Luffy so everybody with a brain knows Luffy will do better, probably even way better (like in Dressrosa or maybe even more since now Luffy has the tool to hit Kaido while Law hasn't it, maybe he can shine a bit by supporting the others but that is already making him a background helper in the end).
Zoro, as a Zoro fan myself I expect for him to do well, scar kaido a bit like Oden but in the end he will not be on par with Luffy, who knows he could even stop fightijg Kaido at a certain point to fight King (or viceversa, forst fight King and then come to Kaido). We will see.
My guess is Kidd since his fans expect him to be a rival if not the true rival of Luffy amd if it wasn't already clear when Luffy saved him and Killer now they will have a rude awakening.
Also there is Sanji who, contrary of Killer, had already lost by not being in the "family picture", even if on one hand he is not a supernova and on the other many already expected him not being there (it is also true that Jinmbe as well was left out so at least he avoided another fatal "new M3" blow) but most likely will arrive later to help.
