Scott Blackwood, 30, was battered, stabbed, stamped on, strangled and tied to a bath before an attempt was made to set him on fire.
Allan Nicol, 36, and Thomas Moore, 26, and Georgina Smith, 22, attacked Mr Blackwood despite claiming to be his friends.
Nicol and Moore were found guilty of murdering Mr Blackwood at Wheatley Road, Saltcoats, on July 3 or 4, last year. They were both sentenced to life imprisonment and ordered to serve at least 20 years each before being eligible for parole.
Judge Lord McEwan said: "This was a scandalous, disgraceful and horrific attack on a young man including what amounted to torture."
Smith, 22, was convicted of the lesser charge of killing Mr Blackwood following a five-week trial at the High Court in Glasgow. She will be sentenced next month.
Mr Blackwood was relentlessly bullied by the mob before he was set upon.
This included an allegation Smith once threatened to pour a mixture of boiling water and sugar over him for no apparent reason.
Mr Blackwood suffered 72 separate injuries including scalds and chemical burns. He suffered 13 stabs wounds and three broken ribs,.
His eye socket and cheekbones were smashed and he was strangled.
Pathologist Dr Julie McAdam said the head injuries found on Mr Blackwood were usually encountered in car crash victims or people who had fallen from the great height.