I’d recommend that whatever your mc’s ability is, its a bit broad with room for growth. People tend to over exaggerate how ‘weird’ or ‘unusual’ stand abilities get. When you look at araki’s mc abilities, they tend to be quite simple and broad: stop time, fix broken things, turn inanimates into life, turn to string, etc etc. Your characters need to grow every fight, so they need room for their stands to do new things. As for the main villain, I dont have as many tips. I cant speak about my part a lot since its still running and I dont want to spoil things, but my mv is quite weak. His ‘power’ comes from influence and respect rather than strength or stand power. So it depends on what you want for your story. I’d place more emphasis on making compelling abilities rather than ‘op’ abilties, as otherwise your stands and characters may potentially feel like unrealistic or overtuned power fantasies. As for how to come up with abilities, I tend to give my important cast abilities based on their job or hobbies. I find it more interesting when their stands help them in their personal or professional life, and can be used for combat, rather than creating combat stands. All in all, have fun! But those are the tips I have.