Pretty much what it says on the tin. Would an asteroid like say, the one that killed the dinosaurs be like a massive atomic bomb? With the eyes melting, bodies burnt to a crisp, leaving only shadows behind, etc. (Minus the radiation)
There's quite a bit of radiated heat when a massive meteorite hits the Earth, so that heat could already 'burn you to a crisp'.
However, with nuclear weapons ranging up to 50 megatons (Product 602 aka Tsar Bomba's, with a design limit of 100 Mt), that energy is already exceeded by a stony impactor in the rather moderate 130 m size range.
The Chicxulub impactor that likely wiped out the Earth's dinosaur population (and a lot others) is estimated to have had a size of 10 km and and an energy of 100 teratons of TNT (or 100.000.000 megatons), dwarfing any nuclear arsenal currently imaginable (short of antimatter weaponry).