Should you forgive a cheater?

I know everyone deserves some forgiveness, but should you always forgive a cheater? Are there some cirstances where it is not forgiveable? For instance a man/woman goes on a business trip and has a fling with a coworker. Forgiveable? A man/woman searches the internet for a ual partner and has a one time fling. Forgiveable? A man/woman has a five year fling with an X. Forgivable? A man/woman searches the internet and has a long relationship with another person and only stops when you find out. Forgivable? A man/woman brings a ual partner into your home and bedroom. Forgivable? Is a brief fling more forgivable than a long term one? Is an affair where the person is allowed into the home and has with the spouse in their marital bed showing more than the need for ? Is this showing some type of disrespect? If a man/woman says they truly love you would they do things which show blatant disrespect or does this show they have some type of resentment/hatred against the wronged spouse?