What is the best way to respond to "You have an answer for everything", "You always have to be right", or "You always need to have the last word"?

When a person says this, sometimes even if they do it in a positive tone, it's usually a way to verbalize more concrete concerns that you should address. For example, they might feel that you are always dismissing their opinions, that you don't listen to them in general, or they would simply like to get support when they express their views in a group so they get some recognition. In any case, they feel like you can do something to help but may not feel comfortable to express it or may not have fully identified it. If that person is important to you, you should be able to see what they want and take action.