Hi @littledevil
You can use the unset() function to delete the row from the returned repeater data. After that, you can use the array_values() to fix the key index. This answer should give you more idea about it: http://stackoverflow.com/questions/369602/delete-an-element-from-an-array#answer-369761.
So, when you update the repeater using this code: update_field( $field_key, $value, $post_id );, it will use the new data without the deleted rows.
I hope this helps.
