You might get this error if you try to delete WordPress.com Stats plugin. This happens when you have installed Jetpack by WordPress.com plugin.
Fatal error: Cannot redeclare stats_get_options() (previously declared in /home/../public_html/wp-content/plugins/jetpack/modules/stats.php:110) in /home/swamid/public_html/wp-content/plugins/stats/stats.php on line 91
I haven’t done a lot of research on this issue so can’t find out the exact reason for this error.
If you have WordPress.com stats and Jetpack by WordPress.com plugins installed and you want to delete the WordPress.com plugin then fist disable Jetpack by WordPress.com plugin then delete WordPress.com plugin and you will not see any error.
Even if you forget to deactivate Jetpack by WordPress.com plugin before deleting WordPress.com plugin then no need to worry. WordPress.com plugin will still be deleted even though you see error.
Ignore the error and go back to WordPress admin and everything should be fine.