How can i file a defamation and harassment case against my ex wife

Hello, I got mutual consent divorce from ex wife abroad where we are permanent residents. She later moved for sole custody of our 6 year old child ( which we agreed to be joint custody during divorce). The court abroad after months of investigation gave me sole custody. Our younger child's custody is with her. A week after that she filed child rape case on me which was dropped after investigation and later district court gave me custody as well. Ex wife moved back to India and filed cases under Pocso on me in Bangalore. It was dropped by police and later child rights commission referred the child to NIMHANS, where doctors found out that in fact mother has been beating and abusing the child. Child right commission decided in my favour and asked ex wife to see a physiatrist and give a report. I now want to file defamation and harassment case on her. Help with maintainability and consequences.