What should I do if I meet a colleague who keeps pestering me to find fault?

obviously, this is the jealousy of your colleague. He may think you are new here, but your popularity is better than his, your work ability is stronger than his, and your boyfriend is good. In short, it is better than him everywhere. So, he was jealous, so he tried to suppress you in various ways, trying to belittle you and raise himself. Therefore, you can completely ignore it. He will only make himself more humble. You should take pity on him from a high angle. Because he has admitted that he is a loser. If you dispute with a loser, you can only be as good as him.