A high conflict personality will use anything to harm the other parent. Usually they are the abusive member of the partnership. Sadly the most effective tool for hurting an ex partner is by taking the children through family court.
They will not mediate, will break all boundaries, will alienate the children against the protective parent, will neglect the child, will make false allegations, they will make contact difficult for you. Their new partner may not be nice to your child. They will force your case into family court. They will pay for and manipulate professionals to try to 'win' points to gain residency. They will not care about the damage they will be doing to the children. If they get residency they will use this to further abuse the protective parent by fabricating issues to reduce contact.
They will never stop.
They will make you look like and feel like you are crazy. And all of their friends will help them. You will feel isolated and confused.
This is a most cruel and ironic twist in high conflict divorce as often the main reason why a protective parent leaves a relationship in the first place is to keep their children safe from an abusive partner. Sadly, too often, residency is transferred to the abusive parent as they have calculatedly manipulated the highly disfunctional family court system and its professionals to ensure they obtain residency and a favorably abusive outcome for the protective parent.
Please see our page titled 'Dealing With Family Court' on this particularly difficult matter.