How to get rid of competitors in google pack?

Theres a competitor buying negative reviews on my gbp
Can i get them banned or anything?
Is it worth to buy negative reviews on his gbp too??
what do i do excpt for letting them delete

That's really a sad situation.

The only thing you can do is report them to Google or hire someone to remove those reviews for you.
And if somehow you can show Google support that these fake reviews are, then probably those reviews won't stick for long.

And I wouldn't recommend you do the same thing your competitor is doing to you.