#1 Dean Ambrose (Left WWE in 2019)
After The Shield broke up in 2014, Dean Ambrose didn't get to experience the same level of success as a solo WWE Superstar that his Shield brothers did. Even though he became a Grand Slam Champion, most of his title reigns weren't memorable.
In 2018, the Lunatic Fringe completed his much-awaited heel turn. However, that turned out to be underwhelming as well. After a segment in which the 2016 Money in the Bank winner had to take rabies shots, Ambrose decided that he would leave WWE after his contract ended. Discussing said incident on Talk is Jericho, Ambrose (now Jon Moxley) stated:
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“This is the day that I knew 100 percent I was gone and there was no turning back. I actually almost walked out. Not really, I’m glad I didn’t because I would’ve ended up in some legal stuff. I knew I was gone in July but I’m thinking, like, why rush it? It’s only eight more months or whatever.”
Less than two months after the aforementioned segment aired, the official Twitter handle of WWE confirmed that Ambrose would not be resigning with the company. This news was immensely shocking as, despite the questionable booking of his character, Ambrose was still perceived as one of the top Superstars.
Fast forward to May 2019, Jon Moxley made his AEW debut and the rest, as they say, is history.