Betrayal to me is a breaking of trust that is detrimental to a relationship. We are all different and our relationships are based on differing values but I think we all know right from wrong. Two ladies moaning about their respective husbands not mowing the lawn or being lazy about the house is not the same as having an affair and lying about it in order to deceive. If any action violates the trust that any relationship has then, at least to me, it must be classed as betrayal.
Having an extra marital sexual relationship, lying, deceiving and constantly belittling or harming your partner is a betrayal of the trust your partner has placed in you. It is not nice in fact I would go as far as to say it is an evil and selfish thing to do.
Mutual respect, love and trust are paramount and sacrosanct in any relationship. If they are broken then the injured party has been betrayed. Any psychological, physical or moral violation of a marriage or relationship is, in my book, a betrayal. It has happened to me and I would not wish it on my worst enemy. The results are devastating for the innocent party.
Specki Constant unwelcome criticism would be betrayal in my humble opinion but friendly criticism which both partners could laugh at would perhaps not be. I think we know what would be classed as mental cruelty as against a term of endearment.