What is a bad trip ?

I’m curious to hear versions of what people consider to be a bad trip. Is it intensity or duration ? Loss of control ? Is it dark or demonic visions ? Anxiety or panic attacks ? Fear ? Negative physical reactions like nausea & vomiting ? Please share your personal experiences (if it’s not too traumatic to talk about or recall).

*EDIT: My deep gratitude to everyone who shared their experience here on this post. I sincerely appreciate every piece of knowledge shared ❤️.