The one that the guilters for the most part believe is the sex party gone awry and that Amanda used her sexual wiles to get both Rudy and Raffaele to help kill Meredith. They make her out to be a cross between Sharon Stone in Basic Instinct and Charles Manson.
It also transforms two young men into pathetic easily manipulated brainless slaves to their own hormones. Never mind there is no history of Amanda ever acting in such a way or Raffaele being that easily manipulated.
In 7 years, I have never heard a logical argument supported by the evidence for a motive for either Amanda or Raffaele, and I'm convinced that I never will.
Once again, the guilters believe this because (IMO) Andrea Vogt passed same-day reports of the prosecution's 2009 case to Peggy Ganong from the courtroom. Like torch-carrying, pitchforked villagers, the early guilters locked into this because it was one of Mignini's early theories - sex-game gone wrong.
Any vestiges of "Satanic Rite" or "Rite associated with Hallowe'en" petered out at trial, for reasons discussed ad nauseam here.
By the time of Mignini's 2009 closing - Machiavelli summarized this just a month or two ago in this very thread - the motive was more psychological/psychopathological. Judge Massei was so impressed by Mignini's factoid-theorizing that Massei substituted a choice-for-evil.
The real lick-spittle in this is prosecutor Crini in Florence. He phoned-in his prosecution case, hardly letting his feet touch the floor by saying this murder was over toilet-cleanliness. This was more of an insult to Meredith Kercher than anyone else - presumable, acc. to Crini - Meredith became so bitchy in her complaints that it led to her murder!!!!
That one was so bizarre that Nencini (how many subs are allowed in soccer?) substituted his own.... reaching back, wayyyyyyy back beyond even the ISC/2013mandated motive of sex-game to Rudy Guede.....
..... the sole source of the "argument over rent money" motive. (By this time the lick-spittle Crini had cashed his paycheque and went to confession to atone for his spineless sins.)
Nencini's genius was to pull that one claim from Rudy, while ignoring that the basis for Rudy being able to hear Meredith's complaints about Amanda (once again, making Meredith out to be such a badguy that it led to her death!!!) was that Meredith had actually consented to a date with Rudy, and had been the one to grant him consensual entry to the cottage.
No wonder ISC/2015 annuled the whole thing, and exonerated AK and RS.
But why then do the remaining guilters, now mainly hidden behind Peggy's wall with the curtains drawn, maintain sex-game or psychopathology? It's no matter now, really.
I don't even know why I'm commenting like this.