The significance of Light Yagami's rivalry with L, Near, and Mello in the anime "Death Note" is that it serves as the central conflict driving the plot forward. Each of these characters represents a different approach to justice and morality, with Light seeking to create a utopia through his use of the Death Note, while L, Near, and Mello are determined to stop him and bring him to justice. This rivalry explores complex themes such as the nature of good and evil, the limits of power, and the consequences of one's actions. Ultimately, it is this rivalry that shapes the narrative and leads to the dramatic conclusion of the series.