Display Something in the Header After All Styles are Loaded

Hook to wp_enqueue_scripts with a high priority number. For example:

function load_my_style_wpse_90225() {
  wp_register_style( 'mystyle', get_template_directory_uri() .'/path/to/stylesheet.css');
  wp_enqueue_style( 'mystyle' );
}
add_action('wp_enqueue_scripts','load_my_style_wpse_90225',1000);

That should reasonably load last in line.

Basically the same answer as here: Wooslider custom css

Refernce

http://codex.wordpress.org/Function_Reference/add_action