what is the sharks only enemy?

Answer 1

'only' means one, but it seems there are in fact two enemies, dolphins are their natural enemies, see link below where I've qouted it from:

"Dolphin (Delphinus delphis) Interesting fact: Very social and intelligent, lives in flocks, the shark's only natural enemy since they can ram their sides with their hard noses"

But off course dophins do not do much damage, man is the real culprit. This link gives a list of the top 30 endangered shark species around the globe compiled from the IUCN list: http://www.bite-back.com/sharks/endangeredsharks.html

The following link gives reasons for shark numbers decline, it seems all sorts of reasons, mostly due to harvesting as food delicasy:
http://www.bite-back.com/sharks/endangeredsharks.html

but also due to adventure tourism/sport,

I also recall environment program that dealt with issue of shark nets being real danger to certain species as well.

Answer 2

Dolphins will beat up a shark , as you might have seen on the tv show flipper.
I saw a video of an octopuss that killed and ate a shark
Humans kill sharks in the tens of thousands per year for shark fin soup, yum yum.

Answer 3

Humans

Answer 4

They once showed a killer whale attacking a great white shark on
a nature program.

Answer 5

The human race

Answer 6

my son did a report on sharks and dolphins can kill them by ramming them with their nose

Answer 7

humans, but there has been sightings of killer whales killing sharks to feed their young as well.

Answer 8

Pollution, caused by Man.

Answer 9

man

Answer 10

woman