As WordPress developers, we’re not strangers to plugins issues, and we’ve encountered several situations where a site went down completely because of them, or at least WP-Admin did.
How can you disable a plugin if you don’t have access to WP-Admin? Easy! Just go in through FTP and rename the folder/file of the plugin. Enter WP-Admin (you’ll be able to do so now) and go to the plugins page, where you’ll see a message saying that ‘Plugin X’ has been disabled because the file does not exist. After this, you can rename the plugin folder/file to its original name.
Of course, before doing this, you need to identify the source of the issue via error logs or some other means!
This can be done easily using WP-specialized hosts like WP Engine, which we recommend wholeheartedly because they fix most of the issues presented in this awesome post by Mitchell Callahan.