Plugin editor crash WP

Yesterday I downloaded a plugin. It needs some modifications to work so I do it using a shell editor directly in the plugin folder. After some tests I realized that any change I do there were ignored by WP ??!?

After, I found the plugin editor in the admin console. The changes there take effect, but not change the plugin files ??!?

The problem is: I have made an error in the PHP plugin code and now any access to the blog (admin pages or post pages) gives the same error:

Parse error: syntax error, unexpected ‘)’

I have tried to delete the plugin but it has no effect (the plugin code is untouched).

What’s happening? How can I disable the plugin?