Should I delete this bad question by self or just put it as a negative example for everyone?
To some extent what you may or should not do is already hard-wired into the site (as what you can or cannot do).
For your question, it doesn't actually matter much — unless it gathers upvotes, it will be auto-deleted in a couple of days. Closed questions are only kept if they have a positive score or if they have an answer with a positive score.
So, unless there is some positive contribution (in terms of question/answer score = upvotes minus downvotes) on a question, it will not be kept as a "negative example".