For all christians, of any denomination: when can someone who has been divorced by their spouse re-marry?

when can someone who has been divorced by their spouse re-marry? On what grounds is re-marriage permitted? If you can cite scripture, it would be appreciated. What constitutes a valid marriage? You can't marry an insane or mentally hanicapped person, or someone who was already married, and both parties have to actually intend to at least attempt to keep the marriage vows, right? what about the person who nievely marriessomeone who is only interested in their money, or who admitts that they would divorce them if they didn't feel in lover anymore, or who is secretely havign an affair before, and after the wedding, or only weeks after getting married has an affair? or one who leaved and abandons their spouse 2 months after getting married for no valid reason? What about physical abuse or of one spouse by the other, or child abuse, or simple abandonment or adultery? How about gross financial irresponsibility and selfishness, to the point of bankrupting and destroying the couple financially for selfish wants? What about if one spouse was never a believer in god, never intended the marriage to ba anything other than a contract, and subsequently leaves the other (for non-religious reasons)? What about if you marry someone and later find out that they are a drug addict, or have already been married and divorced. What if you thought she was a virgin, and after maring her, found out that they were not? What if your spouse aborted your child without tellign you? What about if she was married before and had the marriage civilly annulled, but you married her anyway, or didn't know, and subsequently found out that your church views the first marriage as valid? wht if she was married before, but it is but it is uncertain whether she was validly married in the first place?