The number one enemies are us - HUMANS. Pollution, destroying of the natural habitat, etc, etc…
Besides humans, mongooses are the biggest threat to k. cobras of any age, that's why in some countries people keep them (mongooses) instead of cats. These are followed by owls, eagles, sometimes rats, army ants, civet cats and centipedes. Eggs and baby-snakes face the most threats, as cobra's young offspring is naturally more vulnerable than adults.