I need to decrease visibility of some video on youtube

The problem is some malignant youtuber. He gives bad review for my product ( we have dozens of positive reviews) but this bad review is always on the top of searching results.

We proposed him a cooperation, money - nothing works, he is just happy that he blames us.

Is there anybody able to help?

Well there's your first problem... Offering him money to take the video down makes it seem like you run a really sketchy business. Why not reach out and say something like "Our customer satisfaction team sent me a link to your video and we're terribly sorry the product wasn't what you expected. We'd like to offer you a full refund and see if you'd be interested in receiving x or y related product for free from us a gesture of appreciation for trying it out..." (it's too late now to do anything like that). Then if he's an honest reviewer, which it sounds like he is, he'd probably take the video down or create a follow up of how amazing your customer service is.

We tried that, and we have dozens of positive reviews, but he is on the top of results. We have positive review with 80k views, and this 'bad guy' has 7k , but his always on top...