Justin Lee Collins used details of his ex-girlfriend's sexual past as a "rock" with which to harm her, a court heard.
The TV presenter, 38, had a seven-month relationship with video games public relations worker Anna Larke, who is accusing him of harassment.
Prosecuting barrister Peter Shaw told the jury at St Albans Crown Court, in Hertfordshire, that she was an alcoholic, bankrupt and suffering from depression.
"She's all of the above but she's not a fantasist," Mr Shaw said in his closing statement. "Does it make somebody with a drink problem - who has that relationship with alcohol - incapable about telling the truth on other matters? The prosecution say no, that would be manifestly ridiculous."
The Crown alleges the star was a controlling, sexually jealous boyfriend who made Ms Larke write down every sexual encounter she ever had. Collins says the sex list was Ms Larke's idea to "unburden" herself.
But Mr Shaw told the jury: "It was to haunt Anna Larke because despite this defendant's assurances about what a good thing it would be to do, he used it as a rock against which any self esteem she did have would be dashed."
Collins denies harassment.
In her closing statement, Collins's barrister Sonia Woodley QC asked the jury: "Has this previously pleasant man become a monster overnight and hit her constantly, hundreds of times causing hundreds of bruises? And yet we don't have any independent evidence that that was the case."
Ms Woodley said the jury could not know for certain that Collins's explanation for that fact the sex list was predominantly written in his handwriting was wrong.
She went on to say that Ms Larke kept the notebook after the relationship had ended to hurt Collins. "This was a weapon she could deploy to get back at him and twist as to how it came into existence," she added.