Find spammer IPs (IP with more than 1 unapproved comment)
select comment_author_IP from wp_comments where comment_approved = '0' group by comment_author_IP, comment_approved having count(*) > 1;
Convert to simple ip list using text-editor and REGX
Bulk check ip locations using https://app.ipapi.co/bulk/
Convert to propper format and insert into /etc/nginx/conf.d/blacklist.conf
deny x.x.x.x;
deny x.x.x.x;
allow all;
Delete from MYSQL.