Leos are outgoing and flashy, often grabbing the limelight away from less showy signs. Scorpio wants to be respected and recognized for their accomplishments, and if Leo steals attention away from Scorpio, they'll find it unbearable. Scorpio and Leo are both fixed signs, which means they can both be stubborn when Scorpio wants to be - and they often do. This isn't an impossible relationship, but it will require a lot of compromise and acceptance on both sides. If Scorpio and Leo can pull it off, they'll both be rewarded with a loving, loyal partner who is in it for the long haul.
P.S. Leo girls should be forewarned; there's nothing you like less than being ignored, and Scorpio boy knows it!