#5 Rusev & Lana

At one point, Rusev was one of the most protected stars in all of WWE. As being pushed as the new big foreign heel in town, Rusev took on a year-long winning streak and won the WWE United States Championship. Things went a little downhill following his loss to John Cena at WrestleMania 31, but he was still doing alright for a while.
Rusev has been on a downward spiral, pretty much since 2017. And despite what was supposed to be a one time joke, 'Rusev Day', getting over incredibly well to the point that it was made into a t-shirt, WWE chose not to push Rusev accordingly. Things have gotten so bad to the point now that Lana is actively complaining about both of their positions on WWE TV as of late, neither has appeared on WWE TV in a month now and, including pre-shows, Rusev has lost at 19 consecutive WWE pay-per-views.
Unfortunately, I think it is getting to the point where it may be too late for Rusev to become a Heavyweight Champion in WWE, but he and Lana both have the skills to be successful outside of WWE, both in wrestling and other ventures. Maybe it's time to exercise this.