You'd have to convince Vod he's mistaken to get rid of it. I can't imagine a way that wouldn't take months.
The negative feedback is deserved in this case. Not only for the several loan attempts but for repeatedly trying to scam someone into buying and shipping him a computer which he will pay for later, and then for laughably claiming he will share a bounty of treasure that is apparently buried on his friends land once he has the money to unearth it .
With all these loan attempts and scam attempts exposed, he won't get his negative trust removed but will probably get more and more negative trust lol.