It's fair to say that Marie Antoinette's accomplishments don't exactly leap out of the pages of the history books. Although it's unlikely that she did actually say "Let them eat cake" about the starving peasants begging for food outside Versailles, she's gained a reputation as the epitome of all that was wrong with the upper classes in pre-Revolutionary France: vain, idle, shallow, and materialistic.
Having said all that, I'd venture to suggest that Marie Antoinette achieved some measure of dignity and nobility by her brave conduct during her trial at the hands of the Revolutionary Tribunal. A list of trumped-up charges was leveled at the former Queen of France, including the patently false accusation that she'd sexually abused her own son. Despite such an outrageous slur, Marie Antoinette deported herself with an air of sullen defiance, showing her utter contempt for this travesty of a trial without losing control of herself.
Both the man who made this scurrilous accusation against her and the judge presiding at her trial ended up suffering the exact same fate as Marie Antoinette herself. And by all accounts, neither man conducted himself with anything like the level of dignity and quiet courage displayed by the deposed queen in her last days on earth.