Depends on the scar and the foundation. If you want makeup that will cover pretty much anything, try the theatrical stuff--Ben Nye, Mehron, etc. Foundation/concealer is easier to get a natural look with and you can get it anywhere with a cosmetics section. Unless your scar is very dark, I'd recommend just using regular civilian products.
Tom Petty [Final Fantasy XV] (9%)
Bondage Finch [Bondage Finch Adventures] (12%)
Melisandre, the Red Woman [Game of Thrones] (43%)