#7 The Undertaker (Summerslam 1997 & 1998)
It would be another six years before another WWE superstar main evented back-to-back Summerslam pay-per-views. The Undertaker headlined his first summer spectacle in 1994 when he faced the "Fake" Undertaker. Three years later, The Undertaker came into the event as the WWE Champion.
The Deadman defended his title against Bret "The Hitman" Hart. To make sure there was a decisive winner, WWE named Shawn Michaels the special guest referee. This proved to be a huge mistake. The animosity between Shawn and Bret was firmly established, so if Michaels didn't call this matchup down the middle, he would have never been allowed to compete in the United States again.
It was Shawn Michaels who helped Bret Hart walk out of the 1997 Summerslam with the WWE Championship. Bret spit in Shawn's face and Michaels reacted by swinging the steel chair that Hart wanted to use, nailing Taker for The Hitman to get the pin. This set up a legendary feud between The Undertaker and Shawn Michaels that led to the first Hell In A Cell Match.
Taker was right back in the main event of the following year's Summerslam. The Undertaker faced Stone Cold Steve Austin for the WWE Championship at the culmination of Highway To Hell at Madison Square Garden. Austin beat Taker to retain the WWE Championship. The Undertaker went on to headline this event again in 2008 and 2015.