#2 Roman Reigns is the only Grand Slam winner with the Universal championship
Finn Balor has not held a mid-card championship or a tag team championship. Kevin Owens is not a tag team champion yet. Goldberg and Brock Lesnar were not even interested in any other titles. Hence none of them are Gland Slam Champions yet.
That leaves only Roman Reigns. He has won the tag team championship with Seth Rollins in 2013. He became a World Champion in 2015, United States Champion in 2016 and Intercontinental Champion in 2017, thereby becoming a Grand Slam champion. His Universal championship win at SummerSlam 2018 makes him the only Grand Slam winner to be a Universal Champion.
Edited by Naveen K