Super awesome gist written by my colleague Ronald Huereca. You wanna disable autocomplete on front-end for Gravity Forms, this is just right code snippet for you.

<?php
add_filter( 'gform_form_tag', 'gform_form_tag_autocomplete', 11, 2 );
function gform_form_tag_autocomplete( $form_tag, $form ) {
	if ( is_admin() ) return $form_tag;
	if ( GFFormsModel::is_html5_enabled() ) {
		$form_tag = str_replace( '>', ' autocomplete="off">', $form_tag );
	}
	return $form_tag;
}
add_filter( 'gform_field_content', 'gform_form_input_autocomplete', 11, 5 ); 
function gform_form_input_autocomplete( $input, $field, $value, $lead_id, $form_id ) {
	if ( is_admin() ) return $input;
	if ( GFFormsModel::is_html5_enabled() ) {
		$input = preg_replace( '/<(input|textarea)/', '<${1} autocomplete="off" ', $input ); 
	}
	return $input;
}
?>

Check it as gist: Disable autocomplete on the front-end for Gravity Forms