behaviour that shows (over)confidence
swagger - arrogance
The word ‘swagger’ was once exclusively used to refer to a style of walking characterized by being very upright and swinging one's shoulders in a way that seeks to impress others and demonstrates a high degree of self-assurance. It has since been adapted to also express acting in a way that is arrogant and even pompous. Mostly, but not exclusively, used in a negative, disapproving context.
David used to be insufferably arrogant and conceited, but he lost his swagger when he was unexpectedly fired from his prominent position.
That politician’s swaggering bravado is totally out of place in high-level peace talks. The government should have sent somebody more composed and unpretentious to the negotiations.
The job candidate had a swagger about him that I liked. This role needs somebody who has belief in themself and is not afraid to take chances.