You just have to copy/paste… The code is already written fully, there’s nothing to edit otherwise I would have specified it. I don’t understand what is your issue then, this is all so confusing…
Just add the command and it’s ready to use, but as I said before, the people using the command will have to call the command with the platform and username (including their discriminator if applicable) they play with.
Regarding the best kill streak value, there’s no such thing in the api, data.segments[0].stats.streak isn’t a thing, therefore value is undefined. Follow the steps mentioned here if you want to add data to display, but you can’t invent something that doesn’t exist: