User can control their killing intention and use it to intimidate others, it can be used in two ways:
The user can give off their pure killing intent, affecting opponents, themselves, and others around the vicinity. Particularly strong killing intent can paralyze the victim in fear, causing them to morbidly hallucinate their own deaths, or even kill them by forcing the mind to believe their death is reality.
Suppression and Perception
If the user has mastered control over their emotions, they can control their killing intent by suppressing it, to prevent their opposition from discovering it, thus hiding one's motives and preventing one from being tracked by such emotions.
Anyone who can also perceive a foe's killing intent can perceive the foe's next move and prepare the next appropriate move in advance.
Apathy: by suppressing the intent while retaining desire to kill.
Akame (Akame Ga Kill!) suppressing her killing intent while fighting Zank the Beheader to prevent him from reading her movements.
Kazuo Kiriyama (Battle Royale) apathetically exuding his killing intent, due to his brain damage sealing his emotions.
Kenpachi Zaraki's (Bleach) killing intent manifesting to the form of his spiritual pressure, making Ichigo hallucinate being stabbed; he later grew strong enough to hide it completely unless he wants to be known.
Yachiru Unohana (Bleach) revealing her true sinister nature, exuding so much killing intent that even the toughest Soul Reapers fear her.
Rei Ōgami's (Code:Breaker) killing intent is so powerful, Sakura described it as the eyes of a grim reaper.
Gildarts (Fairy Tail) when getting serious exudes tremendous power with the intent to crush them.
Wahl Icht (Fairy Tail) when he enters Assault Mode, he modified his killing intent to focus solely on Laxus Dreyar.
Neferpitou (Hunter x Hunter) emits a killing intent through its aura that is capable of reaching up to 2 kilometers in length.
InuYasha (InuYasha) in his full demon persona, is so full of killing intent that the mind-reading Goshinki could not follow.
Sasuke Uchiha (Naruto) releasing his killing intent to paralyze Suigetsu and Jugo from fighting anymore.
Kabuto Yakushi (Naruto) exuding a large amounts of killing intent at times, scaring Oboro and his teammates.
When Arlong (One Piece) is angry, his eyes is a reflection of his killing intent.
Hody Jones (One Piece) overdosed on Energy Steroids, making his killing intent overflowing and unstable.
Jin-e Udō (Rurouni Kenshin) is so skilled with using Shin no Ippō, that he can paralyze a person's lungs, causing them to suffocate.
Seta Sōjirō (Rurouni Kenshin) giving his trademark false smile, exuding no killing intent while apathetically taking lives.
During the fight when the Nine-Tails Fox spills into Naruto, (Naruto) Haku was able to sense it, ghastly, the wrath, the bloodlust, stated it was evil itself.
Parasites such as Migi (Parasyte Kiseijuu) can sense, not only the mood of other parasites, but their murderous intent as well.
Nagisa Shiota (Assassination Classroom), though physically frail, possesses incredibly potent natural instincts for assassination that allow him to completely suppress his killing intent to the point that not even highly trained assassins or veteran soldiers can detect it or...
...emit pure killing intent so fierce it incapacitates even experienced killers.
Additionally, years of living alone with his deranged mother and having to both endure her mental abuse and anticipate when her psychotic outbursts would occur has made Nagisa highly perceptive to the inner thoughts and emotions of others, enabling him to easily read their expressions and intentions and gauge their state of mind just by looking at them to determine when or how they are most vulnerable.
Even while smiling serenely, Retsu Unohana, being the first Kenpachi and the most diabolical criminal to have existed within Soul Society, can get people to do what she 'requests' by projecting Killing Intent.