I'm going to make a guy cry by showing up with a picture of his past because he keeps talking trash about my car
Why hurt him that bad? What is is about the picture that you want to show people?
Just a picture from his past that would make him embarrassed.
Just because a person was talking badly about your car does not mean you need to retaliate. Showing people an embarrassing old picture might make people laugh at him, but it will make you look petty and mean. You should consider just letting it go.
It's good for him, he will learn to shut up about people's cars.
You can always tell him to stop rather than making the situation complex and bigger than it really is. It's just a car that we get rid off every 5-10 years.