Nothing, used as a pronoun subject, is the absence of a something or particular thing that one might expect or desire to be present. As a predicate or complement, Nothing is the absence of meaning, value, worth, relevance, standing, or significance. Nothingness is a philosophical term for the general state of nonexistence, sometimes referred to as a domain or dimension into which things pass when they cease to exist or out of which they may come to exist. For example, God is understood to have created the universe "out of Nothing".
Nothing appears in All Star Smashers as a Support Spirit, as an ace class, where you must fight Thin Air at Eerie Woods to obtain it. When fighting The Air, the enemy can never be visible, and since it's literally Nothing, you can't attack The Air. However, it can still attack you. So in order to obtain Nothing, you have to survive the time limit without being KO'd.