Cheater problem

[Sy3rb]

I love to build large worlds with too many plots, after building in some time some person shows up with not 1 but multiple accounts... Destroying the plots and writing insults, changing population to +2 billion or -2 billion, it even said it been playing for 10 years, I noticed many other worlds are destroyed by it, using names like Orca, TheOrca, Kamikaze1014, Adolfhitler, and the list goes on and on..
Last time I made a huge region I made sure it's 1 plot so he can't do nothing and it worked and I reached 100,000,000 population, but I want to allow other people to build too not only solo game.

Thank you.