WordPress wp_dequeue_script remove all other scripts

You will need to dequeue it after it has been enqueued.

function wpse387889_dequeue_scripts() {

    wp_dequeue_script('jquery-tinycolor');
    wp_deregister_script('jquery-tinycolor');
    wp_dequeue_script('splittext');
    wp_deregister_script('splittext');
    
}
add_action( 'wp_enqueue_scripts', 'wpse387889_dequeue_scripts', 99 );