One of my actual biggest wishes for a complex, mature story is that a former rapist joins the heroes' party, fighting for the good himself.
But who, other than you, wants to see that?
A rapist is someone nearly no one can get behind, except for some crazed individuals.

You can kill a person on accident, on impulse, or even out of revenge, yet I still have to see a true maniacal mass murderer join a hero. Warriors are not murderers, it's their "job".

The process of rape lasts for several minutes.. it's not a single action. It's not like you can say "the feelings got the better of me at this moment". There is hardly any reason to include a rapist in any story whatsoever as the "good guy", because he certainly is not a good guy... no matter how "sorry" he is.