uninstalling plugin

I have to uninstall the plugin. I have deleted the plugin files by ftp, but when I try to login, boom captcha is still showing a code and a field to fill with this code. When I enter the code, I’m redirected to the home page. How can I delete the code lines or the files calling boom captcha in order to access my wp dashboard? Answer please…

https://ww.wp.xz.cn/plugins/boom-captcha/