The seven things cats are most afraid of include:

Water sources. Cats typically avoid water sources because water can damage their skin and fur.
Dogs. Dogs may attack cats, so cats are afraid of dogs.
Loud noises. Loud noises can weaken a cat's immune system, making them more susceptible to illness.
New items in the house. New items will attract the cat's attention, but they usually won't touch them on their own initiative.
Strangers. Cats may be frightened by strangers.
Other cats. Even other cats of the same species can trigger a cat's fear.
Wild animals. For example, mice, because of their small size and ease of capture by cats, which makes cats fear them.