That is an incredibly intriguing question, and every one of those situations presents a unique form of fear. The thought of being the most intelligent life form in the universe is scary because it suggests a profound cosmic loneliness. There would be no one to learn from, no one to turn to with our biggest questions, and no higher purpose or meaning to strive toward other than what we can create for ourselves. It’s an existential fear of isolation and ultimate responsibility. On the other hand, the idea that there is a more intelligent life form out there is frightening in a more direct, tangible way. This scenario brings up fears of the unknown, of being outmatched, or of being treated with the same disregard we might show to less intelligent species on our own planet. It’s a fear of losing control and of becoming insignificant in a larger cosmic order.