Hey there Tailz!
There is no one here on Xbox forums nor Microsoft employee's who can block this persons IP address. What you can/should do is file a complaint against this player. You can also control how to avoid another player.
The most important thing is that you contact your ISP (Internet Service Provider) and provide them with as much information you can.
Ddos-attack are affecting all your internet service so i suggest you try assign a new IP address. The easiest way is to leave modem/router unplugged over night.
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