[quote="OneTrueKing"]i mean how would he kill him

[/quote]
Sorry, I misunderstood your question.
I excpect he would try to rip his belly open or perhaps go for the throat.. Simba was lying on his back, exposing his vulnerable belly area, but his throat and neck is pretty well protected by his mane, so yeah.. I think Scar would have tried both. Tear at Simbas belly with his hind feet while biting at his throat at the same time.