Since there have never been any known and proven alien encounters, your question cannot be answered.
Predator, Alien, Aliens Vs. Predators, Predators
Aliens, the second movie.
most frightening
The word meaning "most frightening" is spelt scariest.
Extra Terrorestrial Alien Encounter - 1994 was released on: USA: 1994 (Walt Disney World)
No.
Roswell
Yes, ExtraTERRORestrial Alien Encounter closed on October 12, 2003. It was replaced by Stitch's Great Escape.
The Nightmare Man. Also on blue peter 2010 Elisabeth Sladen (Sarah Jane Smith) commented on The Nightmare Man being the scariest episode.
the most scariest thing in the world is bloody Mary n the graveyard and the green light coming up from a grave.
No, there's no reason to believe Disney will resurrect Alien Encounter. They had complaints that it was too frightening for younger visitors. They converted it to a Stitch themed alien ride, and downgraded the intensity factor.
Roswell