Question

What type of irony is used when someone claims to be the best at something but then does the opposite?
GPT-4o mini
The type of irony you're describing is known as **situational irony**. Situational irony occurs when there is a significant difference between what is expected to happen and what actually happens. In this case, someone claiming to be the best at something only to then perform poorly or in a manner contrary to that claim creates a stark contrast between their assertion and their actions.