Assuming the translations are correct, then Kid isn't the last life he has, he's just one of the final few. But if Kid isn't last then who is? Well judging by the fact that Kid only had a brief interaction with hawkins in onigashima, his voodoo doll probably wasn't made now. Rather, I think it was made when he was still in udon.
If this is the case, then what's the chance that the final doll is actually Killer himself? Its not good enough for Killer to just go for the left arm, that's too obvious. No, in order to win, Killer needs to outright deactive or bypass Hawkins's powers. But how can he do this?
Killer will basically have to go against his epithet of being the "massacre soldier" and defeat Hawkins using non-lethal means. He'll have to incapacitate him without actually hurting him. Zoro has actually done this before, against monet. By using his killing intent, he literally made monet incapable of using her powers effectively.
As we know, Killer is supposed to parallel Zoro in some ways. So what if Killer's ultimate attack takes what zoro did to the next level. What if Killer is capable of using some sort of mental/psychological attack that can defeat an opponent without actually doing damage. Because it doesn't do damage, it won't transfer to the dolls and hence hawkins will be hurt.
What I described does sound a lot like CoC, but I honestly wouldn't put it past Oda to give Killer a form of ACoC. He was willing to die fighting kaido and only submitted to orochi in order to save Kid. The rooftop 5 have also been portrayed as the greatest of the supernova, so it fits.