They were only stopped after they ambushed Levato's ex-boyfriend Pietro Barbini, her school sweetheart and hurled hydrochloric acid in his face and hit him with a hammer.
Mr Barbini had 10 skingrafts and operations to rebuild his eyelid and nose after the attack. He has said that he "may never have the courage to go back out into the world".
The Northeastern University, Boston, student, 22, tried to warn Levato to leave Boettcher, but she had ignored him - and was added to their sickening list, which included men she had merely kissed.
Levato and Mr Barbini had a brief relationship at secondary school, where she was described by teachers as "a model student". Now the "remorseless" pair are serving a 14-year prison sentence for their sordid crimes.
A judge told them they are "more dangerous than any Mafioso or terrorist" because there is "a vacuum where their souls should be".
Psychologists labelled Boettcher, 30, a sadistic control freak who habitually belittled slim economics student Levato, called her 'ugly' and ordered her to lose weight.
The intelligent brunette, the daughter of two maths teachers, first met handsome stock exchange broker Boettcher in 2013 at a Latin dancing night.
She had already completed an economics degree at Milan's Catholic University, and was by then studying for her MBA at the Bocconi, Italy's top university.
Boettcher, meanwhile, was living in his wealthy mother's palazzo, managing her private assets.
Dungeon
Despite the gym-buffed broker having married Gorana Boettcher Bulog, he continued to have lovers and was known to frequent the elite Milan club scene with large sums of cash.
But like the Christian Grey from E. L. James' Fifty Shades of Grey Boettcher had a troubled background: behind his good looks and wealth, he was an unhappy man, whose German doctor father had left when he was very young. He had even attempted suicide aged 14.
But it wasn't just his unhappy background which left Boettcher resembling the character in the best-selling series.
Police found BDSM equipment akin to Grey's dungeon at his home, including whips, handcuffs and chloroform as well as combat knives, acid and a scalpel.
Horrifyingly, when police questioned why he had the medical knife, Boettcher claimed "some girls ask me to carve my initial onto their body", before asking: "Is it a crime?"
Boettner had two disturbing "wounds" tattooed in red onto both shoulders.
Levato's broken-hearted father later said his hardworking and studious daughter changed overnight after getting together with Boettcher.
He brainwashed her
After her arrest he told an Italian newspaper: "Everything has changed since our daughter met Alexander a year ago. She changed from a serene girl who was to being in her own world, consumed by jealousy and using steroids to lose weight for him. Day by day she has become more fragile. She stopped thinking with her head and began to think only of the man she was in love with. He brainwashed her."
nvestigators were told that when Levato threatened suicide Boettcher was insensitive enough to call her father using the words: "Asshole. Break down the door and save your daughter."
Boettcher was possessive and controlling in the relationship, sending her demeaning messages such as "You are so ugly but you made me fall in love with you: penis and brain".
She had cigarette burns on her body, the court heard.
Psychiatric reports found that both were 'manipulative and egocentric'. While Levato has 'a borderline personality disorder', Boettcher is 'sadistic, obsessive and controlling'.
A female witness told the trial how, during a threesome with the couple while on holiday in Greece in 2014, she and Levato had to submit to Boettcher's will.
She said: "He was known as a hot guy that moved around the Milan scene with huge amounts of cash. But he was also strange: he would show you films with men in hoods throttling chickens. He set strict rules for the threesome. We had to call him 'The King' and while he would decide what we could touch, he did whatever he wanted with us."
- Daily Mail
