The Soyuz 2 can carry 2-3 w-87 nuclear warheads to LEO, or whatever the russian equivalent is. I say 2-3 because it depends on how much they want to slow it down for the re-entry, assuming ground strikes are the purpose. If they shaved off a bit of weight they might be able to get a single warhead to GSO, which considering the density of satellites there, could do considerable damage.
Still don't think they're doing it though.