In kayfabe the only ones who can really stand up to Lesnar are HHH and Dwayne Johnson. Reigns is by far the closest thing they have on the active roster though. The loss to Big Show was horribly booked bullshit, but it wasn't that derailing.
LOL, that was some cringe-worthy shit they booked last week. Reigns shouldn't be losing now, at least not to the likes of Show and Kane.