nonentity
A person or thing seen as unimportant or powerless.
A nonentity is a person with no importance, influence, or interesting qualities. If someone dismisses another person as a nonentity, they mean that person has no power, accomplishments, or significance worth noticing. It's a harsh word, suggesting someone is so unimportant they might as well not exist.
You might read in a history book that a king treated his advisors like nonentities, ignoring their counsel completely. Or a story might describe how a shy student felt like a nonentity at a big school where no one knew her name. The word captures that feeling of being invisible or powerless.
The word can also describe something that barely exists or has no real substance. A tiny country with almost no population or resources might be called a political nonentity on the world stage.
It's not a word you'd use lightly, since calling someone a nonentity is dismissive and unkind. But it precisely names that state of having no influence, recognition, or impact.