The account is that on September 22, 1930 a man named Peter Kulaxides was arrested in Athens as he was about to marry for the eighth time, and was charged with the murders of his seven previous wives, killed during the 1920s. He is said to have made admissions in custody, and the Greek press treated him as a Bluebeard.
That is the whole of it. The source is a single encyclopaedia entry descending from contemporary press reports. No sentence is recorded, this roster's own status field says "sentence unknown", no trial is documented, no victim is named, no method is given, and no Greek court record has been located.
Cases of this shape were a newspaper genre in the 1920s and 1930s across Europe, and the announced count of seven wives is exactly the sort of figure that grew in the telling. The entry is retained as a record of the arrest and should not be cited for the murders, which were never shown to have been proved in any forum.
It belongs with Schultz and Furuya Sokichi in this archive as an entry whose entire source base is one paragraph of press-derived summary.