Interspecies Conflict/fear factor
I am only interested awesomeness, abomination, vileness and net factor of fear and terror.
What man Vides more. Hypothetical. It can not happen.
1) be in a cave and meet Shelob
2) be in the woods and meet tyrannosaurus (weight 10 tons length 14 m)
3) be in the woods and meet Utahraptor pack (10 x 700 kg)
1) be in a cave and meet Shelob: Many people have arachnophobia (a fear of spiders) whether or not the spider in question actually poses a real threat. Many of these fears can seem a bit irrational, but can be very real to the individuals experiencing them. Imagine someone with arachnophobia coming across a giant spider like Shelob! This experience will greatly exceed any encounter with a real spider because whether or not the person's fear of actual spiders is rational or not, any encounter with Shelob in a cave will create legitimate fear because the likelihood of death will be extremely high. Even if a person isn't knowledgeable about Shelob's specific traits and abilities (malevolence, agility, venomous stinger, sticky web usage, huge fangs, etc.), the mere sight of a super-sized spider will generate fear in anyone stuck in a cave with one. Even if running toward the cave's entrance is an option, it's unlikely any person will be able to move across the ground fast enough to escape the very nimble, quick, and stealthy Shelob. Once Shelob actually captures her victim, the worst fears will manifest themselves. Knowing for a split second that escape is virtually impossible (and that life is very possibly about to come to an end), the heart will seem to beat out of its chest. One can only hope that when Shelob's stinger plunges deep into the body that her venom will work fast enough to remove consciousness. Knowing what was happening while being wrapped up in Shelob's web would be truly terrifying. The highest level of fear will be from the point that one realizes that Shelob is too fast to run away from to the point that Shelob catches up with her quarry. If the victim is aware of what is going on after being paralyzed by Shelob's stinger and wrapped up by her web (like Frodo was in "The Lord Of The Rings"), the horror of waiting helplessly for the enormous spider to suck the body's insides out will be a fear of great intensity.
2) be in the woods and meet Tyrannosaurus (weight 10 tons length 14 m): There will be some hope here, so the fear will be coupled with the desperation to escape. A Tyrannosaurus has a stride close to the length of an automobile, and its speed has been estimated to exceed that of the fastest humans. In the wide open a person would be doomed once the Tyrannosaurus caught sight of him/her. In the woods, however, the possibility is there for the human to navigate the wooded landscape faster than the theropod (a 10t animal won't be able to nimbly dodge trees while running, and smashing through them will slow the creature's forward speed). The greatest fear here will be when one initially catches sight of the Tyrannosaurus and seconds later is discovered by the dinosaur. As the pursuit unfolds, the quarry will be running with reckless abandon through branches (and likely getting injured in the process). If the human is reasonably fit, the chance of escape is decent. The terror of seeing such a large predatory animal might cause some to freeze in fear (the 3 reactions to a dangerous attacker are fight, flight, and freeze) and not have enough time to avoid the incredibly strong jaws clamping down on their bodies and having numerous sharp, stout teeth puncture deep inside. A Tyrannosaurus of this size can likely swallow a human in a single gulp, so the death will be a quick one. Even for one that escapes, the violent beats of the heart won't abate for quite some time. I must mention that unlike Shelob, Tyrannosaurus isn't evil and will simply act on instinct to chase, capture, and eat what it considers to be food.
3) be in the woods and meet Utahraptor pack (10 x 700 kg): This is cut-and-dry. Death will occur. The Utahraptors will immediately close in on their quarry and rip it apart very quickly. From the point one discovers that the Utahraptors are aware of his/her presence to the point the Utahraptors close in will be the most terrifying section of time in this encounter for the hapless victim. The thought of knowing there's no escape and that a fate of being bitten and clawed to death is imminent is probably the highest level of fear one can attain. As with the Tyrannosaurus, these dromaeosaurids aren't evil, but their agenda as fierce predators is one without compromise.
*in regards to level of fear, the Utahraptor experience will probably be at the top for most, followed by Shelob, and then the Tyrannosaurus. Depending how it plays out, the Shelob experience has the potential to be more fear-inducing than the Utahraptor attack. These 3 scenarios can be described as little hope (Shelob), some hope (Tyrannosaurus), and no hope (Utahraptors). The most horrific death will likely be from the Shelob encounter, but it depends on how aware the victim is once the paralysis sets in. Death from the Tyrannosaurus will be close to instant, so it won't be as gruesome as being ripped apart by the sharp teeth and piercing claws of the Utahraptors. This question is a little "out of the box" for me (please don't ask this with modern animals because I don't want to put a negative slant on any of them), but I hope I answered it the way you wanted me to. *