One of the worst excuses I've also heard to justify cheating is, well, I did it because I thought you were doing it to me.

That's a lack of immaturity and that's also a lack of communication and being open with your partner. those people really need to go see counseling.

To be honest bro my worst is when I asked this girl to be my girlfriend and then I was going through her phone and I saw her text messages and she said I thought we weren't dating that's that

That is the very worst excuse because why didn't you just ask me why didn't we talk about it? So it might be a lie.