Repulsive in Penny Dreadful
Granted, her character spent a lot of time coughing blood into handkerchiefs, but all that aside, she was completely revolting in Penny Dreadful.
It's the combination of her looks, which I found distasteful, and that horrific Irish accent that really drove me crazy. If that's an authentic Belfast accent, then Belfast is certainly the first circle of hell. If they still speak like that in Belfast, I'm sure you could make a case for exterminating the locals and turning the city into a nuclear test site. In fact, take the most attractive women in the world and give them that accent, and they instantly become disgusting, pitiable creatures who should be locked away in dimly-lit basements to peel potatoes. Just hearing that foul debasement of the English language makes me want to lobby the Pentagon to drop daisycutters over the entirety of Ireland, to save the rest of the human race from hearing that loathsome, abhorrent accent.
Note that I'm saying this about the character, not the actress. I Googled Billie Piper, and when not dressed as a tuberculosis-ridden Victorian-era prostitute, she seems like a normal-looking woman.