>Animals generally have no qualms at all about killing or even just mutilating other animals.
Humans generally don't either. Individuals do, but as a species humans regularly kill other humans.
>invertebrates often consume their prey alive
And humans use the oh so humane factory farms.
>cats and other small predators often hunt just for the fun of it, killing but not eating their prey.
>On the more purely painful evil side, invertebrates often consume their prey alive, inflicting agonizing deaths with no issues on whatever they may be eating.
Sharks are caught en mass, the fins cut off, and the sharks dumped back into the ocean to slowly die, for shark fin soup.
Have you heard of trophy hunting? Have you seen the pictures of mountains of bison sculls for the American West?
>Plenty of vertebrates kill and consume their babies, especially when frightened.
Even in our modern "1st world" society, scared teens still abandon newborns in dumpsters. Many societies throughout history did not consider babies "real people" until a certain age because they may need to abandon them if resources were particularly scarce.
>They also often abandon old and weak members of their packs, leaving them to die of hunger or cold or similar deaths.
Maybe you should read stories of cities under siege, famines, wars, governmental collapse, etc. Humans now live nice comfy lives most of the time, unlike animals “in the wild”. Human societies that lived closer to the edge of survival made callous choices about life or death you are spared from.