Demons do not exist. I will stand by those words forever if necessary. If that triggers you, I am sorry. They simply do NOT exist. They are a manufactured fallacy designed to control the behavior of the masses by the patriarchal organized religion world. They are designed to control you.
That said, there are angry angels and an angry angel can seem demonic, and angels are not all about unconditional love. Get that woo woo new age thought out of your head. Angels are the Divine’s army and were created to do the Divine’s dirty work. So, yes, if you run across an angel that has grown tired of trying to reach you and needs you to Wake up, they might present themselves to be very demonic. Cherubims have four faces and run on hooves — horse legs. That is pretty scary and demonic looking. And remember, there is a good reason that the term “avenging angel” is in our lexicon.
But there are no Demons, there are only angels in disguise. And with our pea-sized mortal intellect, we can easily project Angels as being evil. I like to use this example. Have you ever (or you may have done this yourself) witnessed a child who comes home from school after have been disciplined at school for not doing their assignments and they are enraged because the teacher is “evil” or “out to get them” or “unfair?” Same thing with angels, you refuse to do your assignments and work, and then you get consequences and rather than looking at yourself you lash out at the teacher because they were “mean” to you. If you encounter a demon, ask yourself what “you” are missing. And what part you are playing in the interaction, you will quickly find the threat to be replaced by love and understanding if you truly want to learn and progress.
No such thing as demons, but you most certainly enrage an angel and that is never fun. Been there. But I choose to learn as opposed to be a victim. Allowing yourself to be victimized and whining about it is nothing more than an ego issue.