Ooh, this request is super interesting! Doing it in headcanon form! Also, I just sort of assumed the stand’s ability AND appearance are super terrifying! Sort of like Purple Haze I guess, haha.
Stardust Crusaders reacting to their s/o having a terrifying stand
Jotaro Kujo
Usually, Jotaro isn’t easily intimidated. It’s only once that he finds his enemy has the power to overtake him that he is intimidated. But your stand? Not only does it visually intimidate him, but it’s abilities are something he never thought he would come across.
The first time he sees it, he’s a bit shocked. He’s seen many stands in his life, all with their fair share with appearances, but upon seeing your stand he immediately gets bad vibes from it. It doesn’t appear ‘friendly’ to him, unlike some of his allies stands.
Sometimes, he’ll have thoughts about what could happen to him if he one day, somehow ended up on your bad side. While these are nothing more than simple thoughts, it’s something that he hopes he’ll never have to deal with.
It reassures him greatly that you are on his side, though if your stand’s abilities are harmful to others like Purple Haze, he tries to do as much as the fighting as he can so you don’t have to resort to using your stand.
Mohammed Avdol
He won’t outright admit it, but the first time he sees your stand, he’s pretty scared. If anything, he didn’t expect your stand to be as terrifying as it is.
Throughout his life, he’s seen a very large variety of stands, but he’s never seen a stand like yours. His fear later is overcome by interest in your stand.
Being someone who is very interested in stands and their abilities, he’ll ask you to demonstrate the ability of your stand! Though, if it’s lethal, a simple explanation would do to him- he finds it fascinating nonetheless.
Out of curiosity, if you’re fine with it, he’d have Magician’s Red interact with your stand. When he’s not using it to fight, it’s usually a pretty calm stand, so he isn’t very worried about bad things happening during the interaction.
Noriaki Kakyoin
Having never seen another stand until a while back, Kakyoin is very interested in your stand. Even after you tell him multiple times that your stand is very terrifying, he still persists, just wanting to know what his s/o’s stand looks like.
Being quite a level headed person in general, he’s not quite alarmed, although the sight of your stand does send some chills down his spine.
He understands that some stand’s abilities are harmful to the environment, the people around it, or the user, so he simply asks you to tell him what the abilities of your stand are. Although, if you’re okay with showing him your stand’s abilities, he would be delighted.
He eventually grows to find your stand oddly adorable, even endearing in a way. Besides, it’s just the manifestation of your soul, and to him, it’s just another part of you. Your stand also eventually is more friendly to him and Hierophant, as well.
Jean Pierre Polnareff
He’s very interested seeing your stand! Even though you tell him that it’s a pretty visually terrifying stand, he’s still set on seeing it!
Once he does see it, though, he’s pretty spooked out- you were correct. Though, do expect him to dismiss his fear and make up some dumb excuse to hide the fact that he was scared.
Like Kakyoin, he is oddly intrigued by your stand, even after seeing it and being terrified by it. He doesn’t exactly understand why he wants to see your stand more often even though he’s scared of it, but he still asks you time to time to show him your stand again!
Eventually, he does warm up to your stand, not being nearly as scared as it. He never really questions the abilities of your stand, but once he does, he’s in for a shock, to say the very least.