Just watched a video on TV where a herd of walrus defended against a polar bear - they ended up laming him with their tusks while he tried to break through their defensive ring to get to the pups.
As a result he starved to death as he couldnt move fast enough to hunt any more - he could barely walk.
Otara
Incidentally, there’s a few fun stories about fighter jets being taken down by unarmed aircraft, aside from the infamous Wong Wei incident.
During the Gulf War, an EF-111 Raven electronics warfare platform was cruising along just under Mach 1 at buzz-top level. An Iraqi pilot in a Mirage jet spots the plane, and decides he’s gonna bag himself some Yankees. He comes in behind the Raven, and dives in for the kill.
And immediately nails a sand-dune. Unlike the Iraqi pilot, the Raven crew were letting their plane fly itself using a fairly new terrain-following radar, letting the plane make the minor adjustments it needed to avoid colliding with the sand dunes. Apparently they got credit for shooting down the Iraqi plane.
There’s also a story I’ve read about a wargame where they were training C-130 transport pilots how to protect themselves from enemy fighter planes (the rule of thumb was fly very low, very slow, and make sharp turns). Anyhow, this C-130 is being chased by an F-16, and somehow manages to end up on the fighter jet’s six o’clock, and the transport pilot goes on the radio and shouts “Fox Two!” (Fighter pilot lingo for launching a heat-seeking missile)
The fighter pilot’s response sounded KIND of like “Fox Two”, but different somehow… 
This is what John Stuart Mill meant when he described Nature as “red of tooth and claw.”
If you count humans as preying on one another … my husband’s friend witnessed what was evidently a domestic custody dispute in a parking lot. A six foot well-built man was trying to take a small child away from a 5’2" or so petite mother. Apparently he was coming off MUCH worse in the fray.
You don’t mess with mamas, human or otherwise.
Predators certainly aren’t ignorant of the fact that their prey can fight back, which is why they have evolved techniques to minimize risk such as targeting injured, elderly or very young prey and running an animal to the point of exhaustion before bringing it down.
Nature is not cruel, just pitilessly indifferent.
I once saw an Audubon Society nature film in which a weasel approached a gopher hole only to have the gopher chase him away.
Well the saying goes a caged rat’s gonna fight.
For the most part prey animals, if they had the power of reason, could easily take their preditors. The shere weigth of their numbers. Prey animals seem to “think” in terms of the herd. In otherwords it’s OK to lose one, if that one death keeps the lions (or whatever) happy. They won’t attack the herd.
If the Gnus or whatever said “Hey look their are some lions. Let’s get 100 of us to surround and gore them all to death first,” they probably would succeed. But most animals don’t think like that.
Most anyway. Elephants are an exception. They do not tolerate lions. Even if the lions are feeding they will just run them off even when lions show no threat. Elephants just don’t tolerate lions in their space.
Some kinds of aggressive birds, like crows and blue jays will proact and run off cats that are no threat. Many times I’ve seen poor cats dive bombed by blue jays, and they are not attacks. Jays don’t tolerate cats in their territory. But most prey animals do not attack proactivelyt