Everyone is another version of you. Not that other people actually are you, but that we all come from the same source. And that even the behaviors we abhor in others are sometimes our own behaviors.
You might think your sin isn’t as bad as the next person’s, but you’ve probably done something bad that they’ll never do. And you might not even realize you’ve done it. You may have forgotten, or repressed it. You may have hurt someone and not realized it. You’ve certainly done things in your youth that were hurtful. But you received mercy.
Everyone you encounter is still a child in their own way. You owe them mercy, because they are other versions of you. You owe them the same mercy you’ve been given and you owe them the mercy you’d like to be given the next time you make a mistake (which won’t be long from now).