#2 The clue is in SummerSlam's tagline
Ever since WWE has been affected by the COVID-19 pandemic, all of their pay-per-views have featured a specific tagline. A few words underlining the theme of the event. WrestleMania was "Too Big for One Night", competitors had to "Climb the Corporate Ladder" at Money in the Bank, Backlash featured the "Greatest Wrestling Match Ever" and Extreme Rules was a "Horror Show". SummerSlam has one as well.
You'll Never See It Coming.
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This adds a layer of unpredictability to the event, as we do not know what this tagline pertains to. It could be for one specific match, probably involving Braun Strowman and 'The Fiend' Bray Wyatt, or a common theme over the course of the show.
A likely possibility is the finish of Drew McIntyre vs Randy Orton. By now, RETRIBUTION interfering in the match would not be unpredictable. But the manner in which they do could be something we never saw coming.
This particularly pertains to the reveal of the leader of RETRIBUTION. It might end up being somebody out of the blue, vindicating the tagline in the process. SummerSlam could end on a complete shocker.