my friend is being harassed

Your friend will need to report/block each of the accounts that are harassing him. There is simply no way to predict when/why someone sets up an account what they are setting them up for.

Hope this helps.

In addition to above tell you friend do not enter into communications with this gamer just report and block them.

I've been being harassed. I've blocked communications, but they keep making more xbox accounts and harass me further. What do I do, if they keep doing this? I've been harassed for 5-6 months about a year ago, they kept making more account. And now, recently,
I've been being harassed by someone who's friends with my friend. Same thing, block them, they harass me on more accounts. Do I cancel my xbox live? Do I call the cops? Or are you guys going to stop them? Because allowing people to create more accounts to
harass me, or someone else further, is unacceptable.

im being harassed by [Mod Removed] and cant block or un friend him because of this unknown code

To be rather blunt with you, if whomever is allegedly harassing you keeps making new accounts and you don't want to restrict communications then what do you expect Microsoft to do? It's not like Microsoft can read the minds of the people you made upset
and stop them before they do something.