Raiden because she looks generic and I don't like her story, and that despite this, she's mainstream.
Also this will make me sound like I'm one of those Twitter blackwashing people, but I don't like most sumeru characters because they are white. I know Sumeru is based on the middle east and Africa and I know that there are white people there as well, I also know these characters are white because of sales tactics, as in China and Asia white skin is considered attractive and darker or black skin is considered a sign of poverty. Even if you discredit the fact Sumeru was inspired by these regions, as inspiration doesn't mean copying something, I still think a darker skin would suit Tighnari's, Dori's, Nahida's and Nilou's design better. I also think the darker skintoned characters are too pale tbh.