If it kills the host, it’s not a very successful parasite, or it’s a parasitoid as only one other commenter has picked up. It’s not in parasites’ interest to kill their hosts, it usually happens when they infect a non-preferred host and the system responds differently, like the pork tapeworm Taenia solium which doesn’t kill pigs but can be lethal in humans.
If it kills the host, it’s not a very successful parasite, or it’s a parasitoid as only one other commenter has picked up. It’s not in parasites’ interest to kill their hosts, it usually happens when they infect a non-preferred host and the system responds differently, like the pork tapeworm Taenia solium which doesn’t kill pigs but can be lethal in humans.
A superior parasite would keep the host alive for hundreds of years past it’s normal lifespan, while ensuring that nothing of the host survives.