Akame (Akame Ga Kill!) has been conditioned to be a near-emotionless assassin who is notorious for killing her targets in cold blood.
Kurome (Akame Ga Kill!) has been conditioned to be a near-emotionless assassin who is notorious for killing her targets in cold blood.
Kazuo Kiriyama (Battle Royale) is completely emotionless due to brain damage, allowing him to operate at full efficiency in everything, and is considered a demon of emptiness.
Train Heartnet (Black Cat) was known for his heartlessness during his time as an Eraser for Chronos, killing his targets efficiently and mercilessly.
The Executive Militia (Bleach) of the Onmitsukidō are known for their cold-bloodedness to execute traitors.
Ulquiorra Cifer (Bleach) represented nihilistic aspect of death, and as such, showed no emotions.
With eyes like that of a reaper, Rei Ōgami (Code:Breaker) can kill anyone he deems evil in cold blood, ignoring all pleas and reasons.
Yukihina (Code:Breaker) remains stoic whether expressing to avenge his friend's death, slicing through Houkabe's hostage, or blowing a pleading Houkabe apart.
LuluBell (D.Gray-man) is the only Noah who doesn't show emotions or caring at all, mercilessly killing Akuma's if failed to do the task. The only time she ever showed emotions when witnessing Mimi's death.
Hei (Darker than Black) became a Contractor when his sister fused with him, thus (mostly) acting on rationality and logic while not letting emotions get in his way.
Wei Zhijun (Darker than Black) is a Contractor, thus acting on rationality and logic while discarding his emotions. However, he developed an obsessive grudge against Hei, which was unnatural for Contractors.
As a doll, Yin (Darker than Black) has no emotions, however Yin displayed emotions and her own will. Although emotionless she possesses a deep connection to Hei to the point of falling in love with him.
Vegeta (Dragon Ball Z) showing the typical apathetic trait of Saiyans, easily disposing Nappa for losing his ability to fight despite their longtime comradeship.
Broly (Dragon Ball series) crushing his father and his space pod for trying to abandon him on a dying planet, showing a cruel disregard for even a parent who raised him.
Mard Geer Tartarus (Fairy Tail) has long since suppressed his own emotions and believed that emotions are a hindrance.
Euclid Lucifuge (Highschool DxD) became immensely nihilistic and apathetic after his sister betrayed their master Lucifer, to the point he can destroy countless innocent lives without a single shred of remorse.
Kanna (InuYasha) is a demon of void, and has no emotions as a result.
Learning to deny her emotions during her intense training, Chimera (Marchen Awakens Romance) is amongst the most silent and mysterious Chess Pieces.
Loco (Marchen Awakens Romance) suffered an unknown tragedy in her past which broke her spirit. As a result, her eyes and voice alike display no emotion.
Sasori (Naruto) is apathetic and cold due to lack of parental love, and his puppet body is a physical metaphor of an empty and emotionless vessel.
Sai (Naruto) has gone through Root's extensive mental condition and training, resulting in him being almost completely emotionless, until spending time with Team 7 and Naruto Uzumaki.
Sasuke Uchiha (Naruto) cruelly and apathetically piercing through his comrade Karin to kill Danzō Shimura in order to avenge his brother, Itachi's sufferings.
Obito Uchiha (Naruto) shows no sympathy for anyone due to his hatred of reality, causing the death of his mentor and violently attacking his former comrade and friend, Kakashi Hatake.
Kisame Hoshigaki (Naruto) is like many Blood Mist era Kirigakure ninjas, being conditioned to abandon their emotional attachments by killing comrades, something Kisame is all so willing to do.
Madara Uchiha (Naruto) cruelly and apathetically stabs his fellow clansman, Sasuke, for the sake of his own Eye of the Moon Plan/Project Tsuki no Me.
Unlike his colleagues, the Sound Four, Kimimaro (Naruto) very rarely shows any emotion.
After massacring his entire clan, Itachi Uchiha (Naruto) hid away his pain, feelings and secrets for the sake of protecting his brother, Sasuke.
When Bartholomew Kuma (One Piece) became a living weapon, he lost his free will and became a heartless "human weapon".
The Vinsmoke Brothers (One Piece) were genetically modified to have their emotions completely removed to the point they are apathetic even towards their own deaths.
When Shinichi Izumi (Parasyte) had his cells fused with Migi to repair his heart and before the death of Reiko Tamura, he became distant, unsympathetic, and lost the ability to empathize with others, as he not only thinks but feels emotionless like a parasite.
Seta Sōjirō (Rurouni Kenshin) giving his trademark false smile, hiding his emotions and rendering him unreadable.
Yūkyūzan Anji's (Rurouni Kenshin) tragic past led him to become apathetically ruthless towards the evil such as the village chief, ignoring the man's pleas for mercy as he crushed his head.
Gowther (The Seven Deadly Sins) lost all his memories, feelings, and entire sense of self after he removed his artificial heart.
After her dream demon was killed, Yumi (Yumekui Merry) lost all her hopes and dreams, leaving her an apathetic and emotionless shell.
Because of his empty mind, Strings (Yu-Gi-Oh!) is unable to display any emotions.
Having been experimented on and abused for most of his life, Dufort (Zatch Bell!) rarely displays emotion for the world he has come to hate.
Believing his destiny is to cause absolute destruction, Clear Note (Zatch Bell!) is able to do sadistic and evil actions in a calm and near emotionless manner.
After commiting sorocide in the Shiyuu ritual, Yuu Ren (Kingdom) completely severed any emotional attachments to finalize her training as a full fledged assassin of the Shiyuu Clan.
Partially driven mad by suffering, Nagumo Hajime (Arifureta Sekai Saikyou) had abandoned most of his compassion and mercy, killing all enemies in cold blood
When she was human, Hida Nayuta (Hybrid × Heart Magias Academy Ataraxia) lacked any human emotions, feeling nothing for what all forms of life. Even her children meant nothing to her when they had no more uses for her.
As a creature created from collected evil energy, Orb (Marchen Awakens Romance) never shows any emotion or humanity aside from the malevolent houghts of the souls that created him.