#3 Elias
While it seems that the most obvious opponent for Roman Reigns on SmackDown Live would be Elias, considering he attacked Elias on his first night on the blue brand, I hope this isn't what happens.
Don't get me wrong, Elias is a great performer in the ring and on the mic, but I feel he's still not at the level of Reigns. Elias is a good heel, but there seems to be something lacking in him that would make him a great heel.
While he's still a very young performer and will only get better over time, he may not be ready yet.
Reigns' character on television is also one that is pretty serious which may not mesh with Elias' hilarious comedy. Someone like Kevin Owens or one of The New Day members could be better opponents for Elias on SmackDown Live going forward.