#4 AJ Styles vs. Rusev (No Holds Barred)
WWE history dictates that one-on-one matches usually only have special stipulations added to them when a rivalry has become so intense that the two competitors can no longer be contained in an ordinary singles match (e.g. AJ Styles vs. Shinsuke Nakamura culminated in a Last Man Standing match).
So, in the case of Styles vs. Rusev, it would probably make more sense for the first WWE Championship meeting between the two men to take place in a regular one-on-one match, allowing the rivalry to build before possibly adding a stipulation in a rematch further down the line.
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That being said, this match is currently the main attraction of the Extreme Rules PPV, which means it’s likely to go on last, and it’d be a major surprise if the main event of an ‘extreme’ event didn’t have a suitably ‘extreme’ stipulation – even one as vague as No Holds Barred, which is just a glorified name for a No Disqualification match.