#4 Drew McIntyre is beatable
Braun Strowman is the single most protected Superstar on the entire roster; irrespective of gender.
He rarely, if ever, loses clean, and has been built up as this unstoppable, unbeatable force. He essentially single-handedly won the tag-team championships at Wrestlemania earlier this year.
In the Elimination Chamber match, he took finishers from five different men in succession and still wasn't pinned. He is so protected, that it is neither plausible nor probable that he will be defeated.
That was all right when he was a babyface, but it is a problem as a heel. A heel must look beatable. It must be plausible that babyface X defeat the heel because the role the heel plays in the story is designed to get the babyface over. The hero must slay the dragon, or the audience will stop watching.
What babyface not named Roman Reigns can plausibly even mount a challenge against Braun Strowman?
Exactly.
McIntyre, on the other hand, can plausibly be defeated by any worthy babyface. He is a more conquerable villain than Strowman.