and as for your question, i don't know, for example if a person killed another, (not in self defence) for example to steal he's money, and continued to do that, he's kaffer, if he stop it, and know what he did is wrong, and etc... and go back to the right path, god may forgive him
if he worship anything or anyone + god, he's kaffer, if he don't worship god, or don't beleive in god, he's kaffer, however it's he's choice to beleive or not, no one is going to force him to, a person can't be forced to beleive in something, you have to try to convince him, but, if he didnt get convinced, then, nothing, it's between him and god, and god is who will judge him and not any other person, anyway, kaffer doesnt mean a person that must be killed or something, or tortured...