#1 Finn Balor (2016)
We have seen WWE Superstars getting injured before winning Money in the Bank, before winning the world title, or even a month after winning it. But the misfortune of getting injured during the match in which you win the world title, and having to vacate it immediately, is unparalleled.
Finn Balor had hardly been on WWE's main roster for a month when he became the first-ever Universal Champion by defeating Seth Rollins at SummerSlam. It was incredible to see WWE strap the title on an NXT call-up and push him to the moon.
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However, the 'Demon King' suffered a devastating shoulder injury during the match as a result of a powerbomb into the barricade from Rollins. He soldiered on to victory but was in a great deal of pain. Balor opened the following night's episode of RAW and vacated the big red belt, a day after being it's first Champion.
As far as injuries in WWE go, the timing of this one may be the worst. The current NXT star never truly returned to the main event scene after his injury, save for a one-off match against Brock Lesnar at Royal Rumble 2019.
Who knows how different Finn Balor's WWE career would have gone had he not suffered that injury at SummerSlam 2016? For starters, he would have likely had a lengthy reign as the top Champion of Monday Night RAW.