I agree. Nocturne is my longest-lasting main. What makes Nocturne so compelling is his versatility. He was designed as an AD jungle assassin, but his kit lets him be a melee carry or a bruiser as he so chooses. I argue (though I am obviously biased, having mained him since his release) that he is one of the most balanced champions in league. After his first few post-release nerfs - before which he was nearly xin release broken - he has remained viable and competitive with minimal changes.
That said, his very versatility ruins the point. He is not a dedicated right click carry. His burst can be incredibly huge, as is his build-tanky-and-dive bruiser ability.