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Neutered and spayed cats don't typically act this aggressive. Even more unusual is that a 'male' cat would try to harm a 'female' (especially since both are neutered), even if they were still intact.
With this considered, there might be behavior problems produced by too little space, lack of privacy or over-used litter boxes. It sounds like you've got 8 cats (or more?) in one home and unless this is a very, very large home, it could be acting out due to overcrowding.
I'd suggest thinning the society by about half, but I understand if you feel strongly against this. Sometimes it's difficult to put the animal's needs above our own and it may take you some time to make the right decision.
Until then, try increasing the availability of clean litter boxes and perhaps try to keep these two on different feeding schedules or in different parts of the home as much as possible. Put their food dishes in totally separate rooms.
It may also be necessary to have the aggressive male checked for disease or disorder which may contribute to such acting out and could be rather serious if left untreated (or undiagnosed). Tell your vet about his behavior and your concerns that perhaps a hormone imbalance is at the root of it.
I know what it's like to love cats like this , but honestly, I also know what it means to love them enough to let them go. These days, running a cat rescue, I have to do that all the time
Please let me know what you do and how it goes ok?