Is it more befitting to give zakat to a debtor relative—despite the presence of well-off relatives of his, and his being a supporter of "the oppressor"—or to continue giving it to the families of the wronged and detainees, or to distribute it between the two parties?

If your relative has family members capable of supporting him, and the others to whom you pay zakat have no one to support them and are in greater need, then it is more appropriate for you to continue paying your zakat to them. Although giving charity to a relative is originally superior, this preference is not always absolute. A stranger can be prioritized over a relative if the stranger is a neighbor or in greater need. So, if the stranger is in greater need, he is prioritized over the relative. However, if the needy among your relatives and the poor are equal in need, then relatives are more deserving. And if it is possible to combine your relative and those in need and divide your charity among them, that is good.