People who compare you to others are using the representative heuristic, which is a shortcut in the brain that compares things for similarity in order to make meaning from it in the quickest way. This means it is prone to error because it creates stereotypes that are never 100% representative of the original prototype they are meant to represent. As a result comparison of two separate individuals only has limited usefulness really.
So, the key is to first look for the main message in the comparison -what is it that the person is objecting to here? What feature of your behaviour or thoughts or feelings is this person really reacting to? Do I need to respond to it? Do I need to take some responsibility here? Possibly yes! Maybe No! Whatever the answer, you may need to put a stop to the constant comparisons that are obscuring what the real issues are. You can try to ask the other person to give you specific examples about your behaviour rather than bring up old wounds they need to resolve. Its okay to say “I am not that person.” If you are the one comparing, please stop. It is not helpful. No two people are exactly the same. Each have their own motives and intentions. When you judge a persons character based on a negative perspective of another persons character, be prepared to face deep seated hurt and resentment from your partner as a result of your words that you will need to be dealt with and responded to if you want reconciliation.
Comparisons are not helpful. They are a way of putting people down because the person has been pooled into the same basket of other problem people that were not resolved. It also has an air of “I give up, I can’t resolve this, you are a problem” to it, and this will not fix the issues. Focus on real and specific issues that are current instead and the relationship will go better.