I'm not sure I commented on this thread, not sure how to search threads now, but I don't find breed has much to do with it. Different individuals respond differently to situations. But, as far as breeds go: My most on-the-spot to defend of the ones I've had have been Barred Plymouth Rocks, my two heritage lines. Both Atlas and Hector are lightning fast to jump and run when a girl yells. Atlas, being 3 years old, has lethal spurs. Hector has size and youth, but his spurs are small, being only a year old.
My second most ready-to-defend breed was my Delaware rooster, Isaac, however, his method was get the most girls to safety first, leave his sons on the front line, then face the predator head on if necessary.
Just yesterday, a two week old chick in a separate pen with my broody Brahma hen was yelling its head off when we had to pick it up. Hector, in the barn pen, freaked out and was running back and forth trying to figure out how to get out to get to whatever had the chick. So, I have zero doubt about either of those roosters, both from heritage lines, but completely unrelated (Atlas has 1/4 Delaware from Isaac, so he has it on both sides). Atlas has gotten between me and what he perceived to be danger more than once.
One of my most ready to fight roosters was a bantam Cochin I lost recently (old age, I guess). Xander was small, but he didn't seem to know it. He once took on Atlas when a pen accidentally opened up to keep Atlas away from his own large fowl hens and I saw over and over indications that Xander would have tried to defend his hens from just about anything, though being small (with huge spurs, but still...), he would not have been able.
I think my Brahma cockerel might be okay, but he has not been tested yet. He's huge, but no real spurs and no real challenges yet.
ALL roosters mentioned are non-human aggressive. I don't tolerate a flogging rooster here, at least in the large fowl type.
In 12 years of chickens, we have not had a predator loss though we have all manner of predator here, have seen them, seen evidence of some and some in person, some on game camera.