"I think all the time I cheated on you, I'm like Kira" This sentence can be interpreted in several ways. But in my head, I understood that he referred to a person who thinks he helps others, but when he realizes it, he's just hurting someone. Relationship.
"Peace will not be achieved with violence, but try this and it leads to decadence alone, you cannot change everything! But that is the beautiful side of this world!"
The worst sin of Death Note was not to show what a world dominated by Kira would look like, I remember the episode that L died which I was very sad but I thought they would show a world where Kira had total power without obstacles