What’s the scariest thing in the world for humans?
What’s the scariest thing in the world for humans can be the dinofelis. It may have specialized in hunting our ancestors, with a jaw that was very effective at cracking open human skulls. We eventually hunted them to extinction.

Dinofelis resembled sabertooth tigers in their jaw areas, with their upper canines able to penetrate eyesockets. The brain is nutrient-rich so it’s possible they wanted to get to it for good nutrition. Yes predators have favorite “parts” of the prey that they like to eat. Lions will fight each other over access to certain organs.
They also hunted grazing animals may have terrorized other primates.

They had extremely strong necks and shoulders, likely to enable them to carry their kills up trees and hills when need be.
We take for granted our space in the food chain—actually, not always. Some people still don’t understand how dangerous nature is. People in the wilderness walk out into the woods without any form of defense and get eaten alive by bears and large cats.
An easy thing you can do is keep some form of pepper spray with you. Most predators have very strong sense organs on and around their faces. The pepper spray will be like setting their face on fire.