How many other species can afford the time to express empathy as much as humans do? Most of them are just struggling to survive, so it's not like we get a lot of opportunities to observe that behavior.
So two examples come to mind where it wasn't just survival. One, a wolf pack in Yellowstone invades another wolf pack's territory, chases them away from their dens, forcing their cubs to starve to death. And two, the brutal Chimpanzee war Jane Goodall observed between two tribes. A third example could be any ant conflict between two colonies where they could in theory both survive but instead choose to try and wipe each other out. In fact, some ants form super colonies instead of fighting one another.