Death Note is a supernatural crime thriller anime that depicts the brilliant Light Yagami on his quest to rule the world as Kira, the embodiment of brutal justice. To change the world, Light kills off not just criminals, but people who get in his way.
Plenty of tragic and gruesome deaths unfold in Death Note's story, and some are darker than others. The darkest deaths in this anime often involve likable, innocent people being unfairly killed off or dying in tragic, heartbreaking ways. Many of the darkest deaths in Death Note are administered by Light himself, and who sometimes takes pleasure in doing this, though it will catch up to him eventually.
10 Aiber & Wedy
Aiber and Wedy died separately in Death Note, but they died for the same reasons and had equal status as minor support characters, so their deaths can be lumped together. Aiber was introduced as a con man and Wedy made her debut as a master thief, and both were criminals who worked for L in exchange for some leniency.
Aiber and Wedy did their jobs well, but after L's death, Light recognized them as loose ends. So, Light uncovered their real names and had both of them killed, all because they no longer served a purpose to Kira. That made their deaths a bit dark, but Aiber's was darker because his family saw him die.
9 Hirokazu Ukita
The police detective Hirokazu Ukita merely did his job, nothing more or less, as a detective to capture Kira at all costs. He was a respectable cop and person who was brave enough to volunteer for the Kira case, but when Ukita approached Sakura TV to stop Misa's broadcast as the impostor Kira, tragedy struck.
For the crime of trying to interfere with Misa's broadcast, Ukita was killed with a heart attack. Soichiro himself commented darkly that an innocent man was dead because of that broadcast, and later, Light suggested that Misa killing Ukita was no different than a murderer killing Misa's parents in front of her.
8 Arayoshi Hatori
After Light lost his memories as Kira, Rem passed on the Death Note to a businessman who started abusing it for personal gain. Seven more businessmen joined the new Kira at the Yotsuba corporation, including Arayoshi Hatori. He was complicit in the third Kira's actions, but he was also a loving family man with a conscience.
Hatori was pressured into aiding the mysterious Kira, and he wanted out. Unfortunately, Kyosuke Higuchi, the corporate Kira, had Hatori killed just like that, and the other businessmen barely even acknowledged it. Before the Kira business started, Hatori was a happy family man with a good career, but it was all lost in an instant.
7 Watari
Watari, or Quillsh Wammy, was introduced as L's personal assistant and spokesman. He was a famed inventor in England and built an orphanage, making him a notable public figure. There was plenty to like about the innocent and polite Watari, so it felt terrible to watch him die.
When Light made his move, Watari was killed first, dying surrounded by computer monitors in an unknown location. He had no idea how Kira had gotten to him, but it was happening, and it was all Watari could do to erase all of L's data at the last second. He died alone in that room, though at least his body was recovered for burial later.
6 Rem
When Light made his move to finish off both L and Watari, he made sure to tie up some loose ends in the process. Light didn't like how Rem was so protective of Misa, and he feared that Rem would kill him if he made the wrong move. So, Light maneuvered Rem into destroying herself in the process of killing L and Watari.
Rem noted to herself that Light had surpassed the Shinigami with his clever ploy, getting three deaths for the price of two. It was tragic to see Rem crumble away as Light's unwitting tool, unable to protect her beloved Misa Amane any longer.
5 Soichiro Yagami
Light's father, Soichiro Yagami, risked his life more than once to capture Kira and uphold the law as an idealistic cop. Ironically, Soichiro's final mission involved gaining Kira's powers via the Death Note and the Shinigami eyes, and he died falsely believing that Light was innocent.
Soichiro may have died happy, but that just made his death all the darker. He endured years of stress and fear fighting Kira, and his happiness was based on a lie, meaning he died a fool in Light's eyes. This also meant Soichiro was leaving behind a wife and daughter who needed him.
4 L Lawliet
The antagonist himself, L Lawliet, was convinced that he would triumph over Kira in the end, but it wasn't meant to be. L came close a few times, only for Light's backup plans to put him in one last trap from which there was no escape. Just as L started suspecting Misa as Kira once again, Rem killed L and Watari in one stroke.
L died in the arms of his mortal enemy, dismayed that he could never prove his long-standing suspicions of Light Yagami correct. L got so close, only to pass away as Light gave him a mocking "You lose!" smile in the end.
3 Light Yagami
In the end, not even Light Yagami could escape death, and it felt like a total betrayal. Light faced defeat at Near's hands in a dockside warehouse, and not even Light's wits could get him out of that situation as Kira. He pleaded with Ryuk to help him, so Ryuk wrote a name down, but not Near's.
Light was outraged and started panicking when he saw his own name in Ryuk's notebook. It was horrifying to watch the dignified, confident Light Yagami fall apart in his last 40 seconds of life, desperately trying to deny the inevitable. It felt anticlimactic to have Death Note's protagonist die in the end, but it also sent an important message about Light toying with powers beyond humanity's comprehension and the price people pay for hubris.
2 Raye Penber
One of the earliest and darkest deaths in Death Note involved an upstanding, happily engaged FBI agent named Raye Penber. He was personally assigned to investigate the Yagami family, and on the bus to Spaceland, he was tricked into telling Light his real name.
Light wrote down Raye's name to control him, forcing Raye to meet him on the subway and kill the other FBI agents. It was pretty dark to see Raye unwittingly kill his co-workers, then Raye died as Light watched from a few feet away. Raye finally zeroed in on Kira, but was too late to do a thing about it.
1 Naomi Misora
Naomi Misora's death was one of the most tragic, memorable, and darkest in all of Death Note. She was devastated when her fiancé Raye Penber died, and she strongly suspected Kira. Naomi, an FBI agent herself, pursued Kira on her own and got remarkably close to pinning down Light as her fiancé's killer.
On New Year's Day, Light met Naomi by sheer chance, and he realized he needed to kill her. After a failed attempt, Light wrote down Naomi's name and had her end her life somewhere nobody would ever find her body. Naomi was so close to avenging Raye, only to die in obscurity, and her parents didn't even have a body to bury.