Even if you use Akismet, with its powerful antispam filter, you will see that some comments written in Russian are sometimes filtered. And both filters and bot spammers are becoming more sophisticated and complex. I do not know if it will be a solution, it has helped me a lot.
It consists of including a filter of Russian words and characters in the "Black List" of your WordPress installation. In the administration panel you should go to the Options> Discussion section> Black List of Comments.
It should be like this, one letter or phrase per line.