Aries does not cheat because they value honesty and dignity in relationships. Cheating ends things for them, whether they are the cheater or the cheatee.
Taurus is a faithful and unforgiving sign. They will not put up with being betrayed or betraying their partner. To remain loyal, they require love and attention.
Gemini may cheat impulsively but not intentionally. They will not actively seek an affair, but will not pass up an opportunity. Their affairs are meaningless.
Cancer is faithful, but they may cheat with ex-lovers or prostitutes, which they do not consider adultery.
Because of Leo's passionate nature and desire for affairs, he frequently cheats. Because they understand and accept Leo's needs, partners frequently forgive.
Even when a relationship isn't working out, Virgo stays true to the person because they value honesty, respect, loyalty, and integrity. But they have limits to how long they can wait, and they can cheat.
Libra may cheat because they want to see what happens, but they stop when they realise it's not worth it. If you let them cheat once, they might not do it again.
Scorpio might lie or cheat to get ahead and show that they are better. They see relationships as a way to show how good they are. To cheat is to lose interest.