It is truely annoying. I do see people like that a lot on gameflip. I have seen your post on ‘Spamming on Gameflip’ on your 19 December post. They do it everyday because they want their post to sell but usually their stuff barely sells. Fortnite Section is Way Worst.
The only thing is to give suggestions via support or here. Because it isn’t agaisnt the rules to list the items you have. Unless he does not have all the listed items then it is agaisnt the rules.
There is already a post where we suggested that blocking a person should also block all his listing for the person blocking so the person who blocked will not see the blocked person.
However, he just remakes his post and keep reuploading them so that his listings is in the ‘Recent’ first page. If his willing to keep spending his time doing that, then just let him do it.
I am sure Buyers will click the dropdown button and click ‘Cheapest/Online’ instead of looking at just his listing at the first page. Most people would do that.
That being said, creating listing is not agaisnt rules - https://gameflip.zendesk.com/hc/en-us/articles/205739528-Gameflip-Guidelines.
UNLESS HE DOES not Exactly have ALL OF THEM. Putting on Sale a Listing that Seller does not have is agaisnt the Rules. If you have proof about that, you can send a ticket to support so they can clarify that via https://gameflip.zendesk.com/hc/en-us/requests/new
Just a Normal Flipper On Forums 
Have a Good Day.