Brood parasitism is the most vicious, most cruel type of parasitism there is, and nothing can tops it.
Other parasitism, no matter what, allow you to at least reproduce and/or help the colony, and basically fulfill your evolutionary objective.
Fucking brood parasitism even takes that chance from you, by killing your offspring and forcing you to be a cuck, sometimes by threat of destroying your nest.
your entire resources would go to feed a parasite, while depriving you from continuing your lineage (if you get unlucky and get eaten next year; or worse, get cucked again)
Btw, Personally I believe that adopting children is a form of inter species brood parasitism.

Sacculina exists.

Botflies are pretty brutal.

>>5005021
I know this one, but it won’t force you to give birth and raise the parasites while depleting your resources.
It only either transgender you, and take place of your sperm in its own reproduction cycle
>>5005023
Yeah botflies are bad, so any other borrowing parasite, but none of them fuck with your lineage like brood parasites
Even a horse in pain is still reproduces and rear her children. A cucked bird is literally waste her life, feeding and raising an alien baby

Most animals have no concept that sex results in reproduction and can not even begin to comprehend that life has a point, let alone that point being reproduction (or ascending to an immortal spirit) (or destroying all life) (and other human inventions)

Brood parasitism is actually the kindest. Their instincts to raise offspring are fulfilled. They have no fucking clue what happened. At least they didn't get sick and die - that's all they care about.

Most animals are incredibly fucking stupid.

>>5005030
Actually no. If it was the case, then brood parasite eggs wouldn’t need to be harder than the host eggs, they also didn’t need to do mafia shit and kick the shit out of the host nest if they refused to raise the hatchling
Also host wouldn’t abandon its nest, or try to damage the eggs to get rid of the parasites. In addition, cuckoo bird wouldn’t need to mimic the shape and size of the egg either
It’s the cruelest of cruelest in case of cuckoo because host knows it’s a parasite and yet can’t do shit