We will make Mufasa's death seem like an accident...
by a stampede...
Scar was very prideful and arrogant of himself.
Scar's flaw was wanting excessive power through pride and impulse.
Simba turns out to be alive. This makes Scar fear the loss of his power.
Scar realizes that he has no chance and the Hyenas turn on him.
Scar is defeated. This is where Scar meets his unavoidable fate- death.
As Scar loses everything we feel pity towards him because he was always looked down upon and in the shadow of Mufasa. We as the audience can understand that too much pride and ambition can lead us to have the same fate as Scar did.