I know this would be a bit of a stretch, but not too out there. Scar himself was once the head of the Lion Guard and also the 2nd born. Scar might try and tempt Kion to try and overthrow the Pridelands to make himself Simba's successor instead of Kiara (who, in Lion Guard, appears to be more bratty and like TLK Simba than her TLK 2 self.)
Also, if Zira tried to turn Kion, is it too out there to think that Scar wouldn't at least try? (Not saying Scar would use Kion for anything more than creating chaos with Simba and Kiara and then whack him once he is no longer of use, of course.)