Light Yagami's interactions with criminals and victims in the anime "Death Note" are significant as they highlight the complex morality and ethical dilemmas present in the series. Light's interactions with criminals showcase his initial desire to rid the world of evil and create a utopia by using the Death Note to eliminate wrongdoers. On the other hand, his interactions with victims, such as innocent people who come in his way or are collateral damage, demonstrate the dark consequences of his actions and the moral decay he undergoes as he becomes consumed by power. Overall, these interactions serve to explore themes of justice, morality, and the corrupting nature of power in the storyline.