#4 Randy Orton

Randy Orton is set to return on the post-Money in the Bank episode of RAW, possibly to help improve the ratings. He will face off against Edge, whose return has also been advertised. The Viper has not been seen since that exhausting Last Man Standing Match at WrestleMania 36.
Despite losing at 'Mania, Orton remains one of the top heels on RAW. He is still one of the greatest WWE Superstars of all-time. He would pose a very strong threat to Drew McIntyre and his WWE Championship for sure, with a potential encounter guaranteed to produce some great segments.
It has been well-documented that if Randy Orton is interested in a program, he will be brilliant in it. And right now, there are fewer spots more interesting than a WWE title feud against the Scottish Terminator.
It would make for a great dynamic, with the Viper remaining a threat despite not winning a world title for 3 years. If McIntyre defeats Orton, it would be another notch on his decorated belt.