The superlative should be reserved for expressions that are actually true or, when so qualified, likely to be true in the superlative. This is rarely the case when a superlative is used in the introduction of an essay. Phrases such as "nothing worse," "no greater," or "hardly any" are the lazy man's way to introduce a topic. If it helps you begin, then well and good. When you are through with your first draft, go back and write a real introduction. The way forward will be much more clear.