I'm coming to the always helpful BYC community to help me through this very difficult dilemma.
I have 1 hen, a large fowl Sumatra (Kevin), and 5 bantam Seramas. I used to have a Silkie rooster (Toto) who was my Sumatra hens best friend. He was a great protector and sadly, died that way. He was the only one Kevin bonded with. Now, don't get me wrong, Kevin has always been antisocial since her rescue and for her aggression and flightiness, I always blamed it on her former abuse which is most likely still relevant in some post traumatic stress. No one dared to get within a yard of Kevin other than Toto of course.
Together they were perfect, but the two had a knack on picking on one little Serama of mine who happened to have hatched my rooster. My little Serama would endure morning attacks then by at the back of the pack the rest of the day and night. Now that Toto is gone, Kevin has gotten out of hand with her aggression.
Kevin starts unnecessary fights with my little Serama flock. They have free range of the property, but stay far away from each other. They only flock in when a predator is sighted and they run for safety, but Kevin makes it known she gets to be the first one in. Ever since Toto's brave passing, it seems Kevin has nothing to do but harass the littles. It's beyond pecking order at this point. My eldest Serama, D'ove, took her merry time defining the pecking order when introduced to my chicks and once in a while, she'll reestablish her dominance with a quick peck or chase which is understandable. Together they've bonded and learned their places amongst themselves.
Now, Kevin is a completely different issue. She knows she's top of the pecking order: no one even dares approach her, but still she picks fights. And these aren't the pecking order fights, it's the grizzly cock-fighting style fights against my harmless Seramas a quarter her size. I always wondered why D'ove was so terrified of Kevin. To make it even clearer, D'ove will not go outside if Kevin is outside unless I stand with her. D'ove will stay as far away as possible when it comes to sharing space with Kevin. She quakes in fear when she sees Kevin and will even fly out of my hands with screeching cries if Kevin comes too close. She's even been ripping out feathers recently. So today I firsthand saw Kevin grab D'ove by the neck, hold her to the ground, and mount her like Toto forcefully used to. D'ove pain and screams were loud enough to hear from upstairs and since then, I've locked Kevin in her own personal coop (yes, she has a personal coop due to her aggression). Kevin will not harm any human, she runs away if you come too close and forget about petting her, but she'd never hurt a human.
Kevin is my rescue baby and I want to curb this behavior, but D'ove and the others are also my children and it's not fair to them. If I can't stop Kevin's behavior, then I'll have no option then to rehome her since I cannot bear to watch my Seramas endure her abuse. It's not fair to have my Serama flock stressed and anxious. I love all my chickens and have tried almost everything to stop Kevin, but I'm facing the harsh reality that rehoming her may be the best option at this point. Seeing my animals in pain leaves me in pain and constant fear. SOS!