Can't really do anything, if masuk police report also I doubt it will improve your situation also. Seriously, just do damage control and sell as faulty unit because I think the seller would not want to entertain you.

Buying 2nd hand stuffs is like that wan, there's always a risk you have to take and you took it.

This is 2nd hand set wert.... The seller is selling his faulty Xbox which is considered 2nd hand set also.

Still? You can't do anything to the seller. Call him also no use as he would not entertain the buyer. Report also no use because cash transaction that time has mutual agreement. He can argue his case back that after 1 week who knows what the buyer might mod the Xbox and stuffs like that.

Best thing to do, sell it as faulty unit to get some of your money back. The buyer in my opinion is still on the losing side. Don't think he can possibly get the money back from the seller.

Make police report I guarantee 100% the police will not do anything. Even if he finds the seller, very unlikely you will win a case against him. If I am the seller I have stronger points ahead of you to win you in this case.
A nickname online doesn't mean it belongs to him so all your PM are useless, same goes to all the HP numbers he gave you, it could be terminated already.

Lol all of you forumers complaining about justice? Seriously learn how to deal with life because bad things happen to good people also and they get away with it. Doesn't mean every bad people you must go all the way and condemn him to prison

Life is unfair, that's why we must learn how to deal with it. The actual advice is actually move on and stop complaining instead of you guys interpreting as "Do Nothing"

For what you reply? Entertain him izzit? You do not need to justify everything to anybody if you're right