#8 Shinsuke Nakamura

Shinsuke Nakamura had some amazing matches in NXT with the likes of Samoa Joe and Finn Balor, winning the NXT championship twice. However, many of his fans worried he wasn't going to do well on the main roster due to his English speaking skills not being very strong and the main roster being very promo heavy compared to NXT.
Nakamura began his main roster career with a feud again Dolph Ziggler, which was mediocre at best and not the ideal feud for someone starting out on the main roster. Nakamura continued to participate in various other feuds in 2017 with 2 championship matches against Jinder Mahal.
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However, Nakamura lost both of those matches and was pushed to the midcard following said feud with Mahal. Things began to look up for Nakamura after a Royal Rumble win leading to a match with AJ Styles at WrestleMania 34 where Nakamura shockingly turned heel after losing and began a feud with Styles.
Instead of letting the 2 superstars go all out, WWE quickly turned the feud into a joke and ruined what could've been a stellar feud for the WWE championship. Nakamura won the United States Championship against Jeff Hardy later that year, and held the title for 5 months in an extremely underwhelming reign in which Nakamura only had 2 pay per view matches defending the championship.
Despite these setbacks and having far from great feuds, Nakamura's heel turn did help him to be more in his element and made his character far more interesting than it was while he was a face. Hopefully WWE can give him a push as one of Smackdown's top heels in 2019.