Fiona in episode 7 is the best example of what a fully realized Supreme can actually do under crisis
Episode 7 made me realize that Fiona’s biggest strength was not just having the power of Seven Wonders. It was how naturally she used them under pressure like in her battle against James, she doesn’t just spam magic and you can tell she reads the room by reviving his henchmen back (they were all killed by the coven), turns them against him through concillium then immediately revives Cordelia. The way she utilizes magic is so effortlessly natural like it was a second nature for her.
I have no doubt she’d straight up prevent Apocalypse before Michael come into his power. She clearly had the power, experience, instinct and confidence to be an incredible Supreme if she actually cared about the job. It’s lowkey tragic how she squandered the chances to be the greatest Supreme ever in the history of Salem coven due to her own selfishness because the Coven would definitely thrive under her reign.