I also hated both of them *g* I wouldn't necessarily say that Kennedy was completely pointless (although the forced romance with Willow was IMHO). But as one of the more gung-ho potentials I guess she filled the role of showing that some of them actually wanted to fight and had the slayer spark within them? But she made my teeth grate with the way she spoke about Buffy and the way she ordered the other potentials around. I've never forgotten her gloating at calling Chloe a maggot and being one of the causes for Chloe hanging herself, what a nasty little bully

Riley to me was worse though because so much of the emotional focus went to him in season 4 with the Initiative arc and I just did not care. It felt like him and his issues took over that season at the expense of Buffy