One of a Kind
This error is so common, you probably won’t get the joke at first, except maybe for the hint in the post’s title.
Second panel. The teacher is deliberately (I assume) repeating the student’s incongruity in the first panel.
Unique is an absolute. It means “one of a kind,” period, so modifiers like ‘somewhat,’ ‘more or less,’ and so on, are semantically incorrect. Get it now?
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