While it's not a deal breaker, like anything else in a story, I'm hitting the back button if it's handled ineptly. Cheating is a huge fucking deal, almost always with consequences (unless the cheater keeps it an ironclad secret then it's all on them only), and it shouldn't be used lightly, though I possible even more detest the "automatically unforgivable FOREVER!" mentality. It's too black and white and ignores the fact people do go through this and recover.