#1 Brock Lesnar
Nobody can deny the fact that Brock Lesnar is one of the most stiff wrestlers in WWE. Since his return to the company in 2012, Lesnar has busted open a handful of superstars such as John Cena, The Undertaker, Randy Orton, and Roman Reigns. Due to his MMA experience, Brock Lesnar is portrayed as a brawler, relying more on his strikes.
However, the Beast Incarnate is infamous for his stiff wrestling style. The first incident occurred on Lesnar's second appearance on Raw since his return in 2012. Lesnar was involved in a brawl with John Cena in which Lesnar landed few stiff shots on Cena. The Anomaly even busted open the Cenation Leader in the first few minutes of their match at Extreme Rules in 2012.
At SummerSlam 2016, Lesnar defeated Orton via TKO after continuous elbows to the latter's head. Orton was seen bleeding heavily from his head as the elbow shots cut him open.