Big cat stopper
The small cat took to it immediately.
Probably should've done that a LONG time ago.
PRELIMINARILY speaking, it's marvelous.
My constant supervision has helped over the years, sometimes they even
play (while supervised), but my aggressive cat's natural tendency is
always lurking. She is a great cat to people, she is not really a bully,
she's just ETERNALLY AGGRESSIVE against anything that moves and isn't 10
times bigger than she is.
I found another humane way of stopping my big aggressive cat from
constantly annoying my smaller cat. It will require testing, but it
looks promising. Just leave a door (bathroom with a view to outside, or
whatever) open enough for the smaller cat to get through but not big
enough for the larger aggressive cat. That should work if the victim is
much smaller, like here.
That would be nice since it would be on demand.
Other such possibilities would include some sort of ramp/bridge that
only allows a certain weight...
The small cat gets lots of use out of the Skyway where the aggressive
cat is mostly prohibited from going.