Anime may be filled with all manner of warriors and superpowered aliens, but there's no comparison against the elite and few of the anime assassin. Stepping away from the gaudiness of giant laser beams and explosions, the assassin is a much more subtle fighter, opting for the silent arts of killing.
This involves hand-to-hand combat, simple knives, poisons, and anything that just happens to be at hand. Minimalism is the name of the game, with the better assassin being marked with how much more they can do with less. There are a lot of anime characters in the paid killing game; but out of the genre's best, who has had the more literal band for their buck?
10 Reborn (Katekyo Hitman Reborn!)
Reborn doesn't have a lot of on-screen kills in his career. And while a lot of that may be due to the age rating of his particular series, it's not as if Reborn isn't plenty capable of getting the job done. Ranked as "The World's Strongest Hitman" in his world, Reborn has always been a skilled and dangerous assassin, despite his appearance for most of the series.
Even in his baby form, Reborn has the strength and martial arts abilities to take on opponents more than twice Tsuna's size; and with his shapeshifting, chameleon gun, Leon, Reborn is able to fire a variety of magical bullets whose abilities range between powering up his allies to numbing all bodily functions of his target.
9 Risotto Nero (JoJo's Bizarre Adventure: Golden Wind)
Risotto Nero was the leader of Passione's Hitman Team and the group's most elite assassin, an impressive title in a group filled with powerful killers. Having carried on the assassin's life since he was 18 and responsible for the top hitman jobs of a mafia group, Risotto must have a hefty body count under his hand. This is easy to consider after seeing his fight with Doppio.
Despite taking on the big bad of all of Passione, Risotto Nero was able to hold his own with both his wits and combat ability. He even had Doppio on the ropes with his lethal stand, Metallica. With the ability to manipulate iron and magnetism at will, Risotto is able to craft weapons from midair or, better yet, inside the bloodstreams of his own opponents and even turn himself invisible.
8 Himura Kenshin (Rurouni Kenshin)
Rurouni Kenshin is about a skilled samurai who tries to live a life of a peaceful warrior, going as far as to utilize a blade that can't even cut people. However, that life of peace is only his attempt at redemption after a life of war and murder. After being rescued at a young age by a talented swordsman, Kenshin trained the gentle yet devastating sword art of Hiten Mitsurugi-ryū.
Despite his master being a peaceful man, Kenshin left to fight in the war and became a famous assassin. He even earned the name "Battosai the Slasher" after killing more than 100 warriors during his first six months. Continuing that legacy over the course of the war, Kenshin certainly became an assassin deserving of severe atonement.
7 Koro-sensei (Assassination Classroom)
Koro-sensei is the funny, beloved teacher of Assassination Classroom. With his eccentric style, dedication, and vast knowledge, he was able to teach an entire group of disgruntled kids to believe in themselves. Unbeknownst to them, Koro-sensei wasn't always an admirable teacher or even a powerful, tentacle creature. In his past, he was a legendary assassin that went by the name "The Reaper."
Having worked nearly his entire life as a killer, Koro-sensei was respected and feared by his mercenary peers. Though he never used these abilities against his own students, he became even more powerful after some government experiments and enacted that strength to wreak vengeance on the lab that tortured him.
6 Hassan-I-Sabbah (The Fate Series)
Hassan-i-Sabbah is a name shared by several characters in the Fate series. They are actually nineteen elite assassins whose legends seep deep into Middle Eastern history, killing countless enemies and manipulating the political landscape to their whim. Whenever someone summons an Assassin for the Holy Grail War, they are always near guaranteed to summon a Hassan-i-Sabbah.
Staying true to form, each Hassan-i-Sabbah are faceless killers who stick the dark, focusing all of their efforts to takin on their enemies at their advantage and seemingly always target Masters first. The most powerful and most skilled of the bunch may likely be King Hassan or "Old Man of the Mountain," the original Hassan-i-Sabbah who started the dark order and can even take on other Servants head-on.
5 Akame (Akame Ga Kill!)
Akame may look cute, but few people ever get a second chance to get a good look at her. Having been raised by the Empire and elite assassins since she was just a child, Akame has become a deathly killer who knows how to take an opportunity when it comes. Prior to joining Night Raid, Akame used her assassin abilities to kill countless enemies to the Empire, taking up a legacy as the nation's best assassin.
She has the superhuman strength and speed to take on Akame ga Kill's superpowered, fantasy world, and her Teigu, Murasame, has a deathly poison that can kill any opponent with seconds, an enviable weapon for any killer.
4 Silva Zoldyck (Hunter x Hunter)
Silva Zoldyck is the current patriarch of the Zoldyck Family and head assassin of a family pretty famous for killing people. While the exact extent of his career remains unknown, the Zoldycks are known for taking on nearly all manner of assassination jobs, entrusted to kill anything and everything between entire political opponents and even the entire Phantom Troupe.
As the father figure, Silva Zoldyck has the power and monstrous strength that made the Zoldycks so feared and rivaled that of the Chimera Ants and even Chrollo Lucifer. He personally brought up his children, each an assassin responsible for the deaths of countless people.
3 Rob Lucci (One Piece)
Rob Lucci is likely what every government institution would want out of an assassin. He's cold, dedicated, lethal, and knows how to keep his mouth shut for years and years. Having been trained by the World Government ever since he was at least eight-years-old, Lucci has been raised around the assassin life for nearly his entire life, rising through the ranks to become Cipher Pol's greatest hitman.
At the age of thirteen, Lucci was willing and able to slaughter an entire pirate crew as well the 500 soldiers that they were keeping hostage. Within the current story, he's still a cruel and tactful assassin whose martial arts abilities and leopard strength could rival even Monkey D. Luffy's.
2 Hei (Darker Than Black)
In Darker than Black, Hei the Black Reaper is one of the deadliest assassins around and a well sought after Contractor. Having worked all of his life to protect his sister while in the Syndicate, Hei trained hard enough to develop the strength and killing abilities necessary for keeping up with his sister Bai's development.
Once he unwittingly fused with Bai, Hei gained the ability to manipulate molecular structure at will, frequently manifested as the electrical bursts that he uses to kill all of his enemies. However, the full extent of this power lets him manipulate matter, short out entire buildings, and, in one instance, destroy a huge portion of South America.
1 Light Yagami (Death Note)
Few assassins or even anime characters as a whole are responsible for a higher body count than "Kira" Light Yagami. With the power of the Death Note, Light became capable of remotely killing anyone by simply writing their names.
He used this power to kill hundreds upon thousands of criminals across the world, believing that he was cleansing the planet. However, once he started seeing opposition by some of the world's government figures and detectives, he began even killing those who started to get too close. A revered assassin in both power and intelligence, Kira didn't become a god, but he was feared all the same.