I remember having a soft spot for Rona the first time I watched this season- looks like I might be in the minority there, though.
TBH, I don't think there are any potential slayers that I particularly dislike, but there's really only a handful of ones that we know enough about to like or dislike. Kennedy, Rona, Vi, Amanda, Molly. We don't really know much about Chao Ahn, as most of her appearances tend to be focused around the language gap separating her and the others, and the misunderstandings caused by it, rather than her actual personality. Chloe doesn't appear very much either.
If I had to pick one, TBH I'd probably go for Kennedy. She's a lot like early season Buffy in some ways- she's quite blunt, she speaks out with her opinion, she's not afraid to call out authority figures on their actions, and she's in there ready for the fight when it matters. Since I have spoken about missing early season Buffy in the Buffy we see in S7, it's kind of nice to see a character who exemplifies a lot of the same traits, even if we're seeing them from the perspective of the authority figure instead of her in this case.