Why do lions and hyenas hate each other so much?

It's like their the only two animals who are rivals and hate the hell out of each other, well leopards and baboons hate each other as well but why is it the lions and the hyenas who have beef more than any other animal on the planet? It's like the moment hyenas spot a male lion their ready to flee but with the female lioness it is time to have a battle, why is that? and why are hyenas the only mammals to kill their siblings like right after birth? and why do they eat each other when one dies? btw i'm hoping to become an animal trainer and work a lot with the hyenas and the lions (my two favorite animals).