I say murder, but I think torture - were it an option - is the worst.
Rape is obviously horrific and mentally scarring, but as far as I can tell most victims eventually recover and continue living their lives as normally and prosperously as possible. Murder is, of course, fatal, but at least it isn't particularly prolonged.
Torture, in its worst forms, is something that no-one would ever recover from, no matter what. I wouldn't wish it on the very worst of my worst enemies. So I vote that.
But whichever it is, one thing that we can unanimously agree on is that anyone who does even one of these things in its mildest form is utter scum. And a few other, less dignified words, too.