Can’t stand seeing dogs or cats get killed, but I’m desensitized to everything else.
Nature is brutal. An animal will not immediately kill if it isn’t necessary, as that would be time and energy wasted. Immobilizing prey is just as good as killing it, from the predator’s perspective.
For example, Hyenas eat the ass of their prey first, as that’s usually the first thing they can latch onto when chasing from behind. They eat the ass end first while the prey is still alive, screaming and flailing which turns to whimpers and twitching. The ass is, of course, a long way from the heart and brain, so the prey will only see rest from this torture after they lose consciousness from blood loss, which will be quite a bit after the hyenas start tearing it apart.
Kelp Gulls will land on the backs of baby whales and peck away at their skin and blubber, deforming the calf at best, and giving it a slow torturous death at worst. The calfs don’t have as great a lung capacity, so they need to surface much more frequently, and while mature whales will know to to flick their tail, arch their back, roll around, etc, in order to get the birds off of their back, the calves are not yet smart enough to do so, so they just sit there and let the gulls peck away at their flesh.
I have seen a video of a Coconut Crab breaking both wings of a Red-Footed Booby with its claws before eating it, the bird bleeding and screaming the whole time, while several other Coconut Crabs approach to join in after the bird became immobilized.
The Shoebill Stork almost always has 2 chicks per clutch, and those chicks start pecking and fighting each other as soon as they hatch. The mother only feeds the one that wins, the other is ignored and eventually staves to death.
The term “Brood Parasite“ is used to describe bird species like the Cuckoo and the Cowbird who, after laying their eggs, drop their eggs into the nests of other birds. Oftentimes the parent of that nest will mistake the egg for its own, and will raise the parasite long enough for it to become self-sufficient. There have been documented cases where, if the nest‘s parent does not fall for it and gets rid of the egg, the egg’s parent will come and destroy all of the nest’s eggs while the nest-parent is away in order dissuade them from rejecting anymore parasitic eggs, kind of like the mafia. If this wasn’t bad enough, these Brood Parasite species often have a much faster growth rate than most of their victim species, allowing their chick to hatch and grow such that they grow enough to start pushing out the other eggs and chicks, killing them. It already instinctually knows to do this at a very young age; It commits these murders while it’s still just a pink blob that has no feathers and still can’t properly open its eyes.
Suddenly a house-cat swiftly killing a mouse or bird doesn’t sound so bad, does it?