My choice would be Kevin Owens. Brock vs KO could be pretty enjoyable - Brock arrogantly underestimates Owens (like he did with Eddie Guerrero back in the day) and suffers for his hubris.
That’s kind of an odd way to view it, considering the fact that Brock ultimately won the feud with Goldberg and, in doing so, began a 500+ day reign as Universal Champion, including a match where he retained the title in the Wrestlemania main event against the only other man to beat the Undertaker at Wrestlemania (and the face of the company) Roman Reigns. Every match Brock has lost, including the loss to Goldberg, has been presented as a fluke or an incredible upset. The ‘rub’ is still there. In fact, if anything, Brock has been more dominant since taking that loss to Goldberg - he’s beaten Daniel Bryan, AJ Styles, Braun Strowman, Samoa Joe and Finn Balór with relative ease, and absolutely squashed Kofi Kingston And Cain Velasquez. Seth is the only thorn in his side but he’ll no doubt crush him on the road to Wrestlemania to get his win back.What is this notion of "The one to beat Brock Lenar"? It has already been done by Goldberg in Survivor Series 2016. The rub of the streak and beating The Beast went there, everything after has been yet another statistic. As far as the Miz goes, absolutely not.