#1. Seth Rollins - 2019

WWE continued their efforts to coronate Roman Reigns, but after his unfortunate leukemia announcement, the company had no idea when their biggest full-time star would return. Given the seriousness of the issue, they would have had to operate under the assumption that he wouldn't be returning for a long time.
Seth Rollins was the natural pick to take his spot and was always the second-most pushed full-time Superstar behind Roman Reigns. His momentum would lead him to a Royal Rumble win in 2019 before challenging and dethroning Brock Lesnar at WrestleMania 35.
How Brock Lesnar ruined another wrestler's career - Watch Now!
He would lose the title back to Lesnar a few months later via a Money in the Bank cash-in, which led to a rematch at SummerSlam, where Rollins became one of the few Superstars to pin Brock Lesnar clean. Despite this, his popularity would dwindle a month later after making unpopular comments on social media.
Many fans also felt that The Architect was stale as a babyface Champion, leading to him dropping the Universal title to 'The Fiend' Bray Wyatt a month later and turning heel before the end of the decade.
A top WWE star is missing in action