Several Origin Path options grant the Enemy Talent (some may grant Rival too, but I haven't noticed it). As written, having one of these Talents imposes a -10 penalty to Fellowship Tests when dealing with the noted group. As written, there's also no real difference between Rival and Enemy (and the first is not a prerequisite for the other). I'm planning a rather simple House Rule to address this:

Rival (x) is a prerequisite for Enemy (x). If you have an Origin Path that grants you the Enemy Talent, you instead gain the Rival Talent. If you have a second Origin Path option that grants you Rival (x) again, you gain the Enemy (x) Talent.

For example, let's say that a character takes the Hunter (Hunted) option from the Origin Path and selects Rival (Inquisition) . Next he selects the Darkness (Forbidden Knowledge) option from the Origin Path and he now gains Enemy (Inquisition). He could have instead opted to take Rival in a different group, but for this example, his background is based on really pissing in the Inquisition's Cheerios.

Note that it is possible to still be on non-hostile grounds with a Rival, or even an Enemy. The Talent will simply make non-hostile interactions with the noted group(s) more difficult.