What makes you affraid of aliens?

Ok so a friend asked me to write a horror story about aliens so she could read it in her yt channel, but I'm not really affraid of aliens as I am of other stuff, so I'd like to hear how you guys feel about it. Is it the monstrous appearance? The eminence of a war? The high dangerous technology they might have? Like if all the buzz going on rn about the government hiding UFO sightings is real, what terrifies you the most about it?