My experience has been that it still has paid off to stay consistent. My youngest one is also extremely stubborn with a rage issue (I wouldn‘t dare to say 1% but at least 5%), and I can‘t count the time outs I‘ve had to distribute. All of them as a consequence with advance warning. Partially it was borderline violent, but I‘ve always did my very best to only use as much force to not hurt her, but just keep her from hurting herself and others as well as escaping the isolation from stimuli (I‘ve always stayed with her the entire time). One time I carried her screaming and shouting through a whole restaurant of people and stayed a whopping 20 minutes in front of the door until she was calm and my food was cold.

At the time, it looked like no progress at all, but fast forward 4 years and she‘s 7 now, well behaved, thoughtful, but still confident and strong willed: the upside of stubbornness. I feel like we did a decent job there.