For me, the one and only thing that determines whether a rape scene is highly erotic or utterly lame is whether or not the victim seems genuinely distressed.
Therefore, the most important thing in rape porn is the acting talent of the woman.
Which rape porn star is the best actress?
In my opinion, there is a clear winner: Nanami Kawakami.
Other porn stars whose acting in rape scenes is very convincing are: Iroha Natsume, Hitomi Tanaka, Carter Cruise and this Russian girl:
https://motherless.com/6A9BDA6
What other porn stars have you seen whose acting in rape scenes is really good?