#4 Braun Strowman either enters the Royal Rumble or helps Finn Balor defeat Brock Lesnar

Braun Strowman was initially booked as Brock Lesnar's opponent for the Universal Championship match at Royal Rumble. But he ended up destroying Vince McMahon's limousine, which apparently led to him losing his title shot.
Finn Balor later won a fatal-four-match on Monday Night Raw to become Lesnar's new opponent.
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Braun Strowman doesn't have a match for the PPV and he isn't announced to be in the Royal Rumble match. But any WWE fan would know that he will surely make an appearance. He wrestled Balor on Raw which means he is also now cleared to compete.
I think there are two things that Strowman can do at Royal Rumble. First one is that he might simply enter the 30-man rumble. He could either hijack it or win it. There are many ways to go about it. Another one is that he helps Finn Balor defeat Brock Lesnar.
As he said on Raw, Balor must defeat Lesnar. So he might end up being the guy who will be responsible for Lesnar's loss.