L Lawliet (Alternate Universe)

Origins
At the age of eight, L was found by Watari and taken to the orphanage known as Wammy's House, a home for gifted children. Sometime after, Watari realized that L had incredible intelligence and later assisted him in his cases. L became a detective at a young, unknown age and eventually gained a reputation as the greatest detective in the world whose opinion is highly valued.

L notices the rapid rate of criminals dying of heart attacks, and suspects a person is behind this and that he is in Japan, so he seeks cooperation from the NPA. He begins the Kira case by having undocumented death row inmate Lind L. Tailor introduce himself on television as "L" and say that Kira is "evil." This provokes Kira into killing Tailor on the spot, which in turn confirms that the Kira killings are not a coincidental succession of heart attacks amongst criminals but the designs of an ingenious murderer who will kill any and all who try to stop him. It also reveals Kira's location, since the broadcast was televised only in the Kanto region.

Personality
L's most prominent character trait is his secretiveness. He rarely goes out into the outside world when not investigating a case, never shows his face to the world, and communicates almost exclusively via his assistant and only friend, Watari. When meeting face-to-face with others, he never gives out his real name, instead using a variety of aliases, such as "Ryuzaki" (when interacting with the Japanese task force), "Hideki Ryuga" (when meeting Light at his school), "Eraldo Coil" and "Deneuve" (under which he has developed reputations as the world's second and third-greatest detectives). Additionally, due to having minimal interaction with other people, L has very poor social skills, and is prone to performing actions or having habits considered rude and inappropriate, including eating with his mouth open, talking with his mouth full, placing feet on furniture, biting fingernails, etc. L also has several quirks, such as preferring to crouch rather than sit, eating only sweet foods (like desserts, candies, and fruits), and holding items by using only a thumb and a finger.

Despite his disheveled appearance and odd habits, L is highly intelligent, and has a keen mind rivaling that of protagonist Light Yagami. Although he doesn't have any good social skills, L has an analytical understanding and knowledge of human nature, which he uses to his enemies' disadvantage, such as when he tricks Light into killing an impostor of himself on live TV and pinpointing his whereabouts to the Kanto region of Japan (since the broadcast was only airing there at the time), betting on the slim chance that Kira would kill someone who made a stand against him. He also creates false information and leads to try to bait Kira into revealing himself, which nearly succeed. When presented with any information, L tends to meticulously second-guess anything he's given, and analyses it for any inconsistencies or clues.

Although he's trying to catch a murderer, L is not above using questionable or brutal methods to get answers, making him an anti-hero. While he never kills anyone himself, he's not above keeping Light and his accomplice (and lover) Misa Amane in solitary confinement for more than 50 days to test whether they're Kira or not. Earlier in the story, he took a criminal on death row and made him act as a decoy to draw Kira out. Later, when confronting other Kira (Kyosuke Higuchi), L made it clear that he was willing to torture him to get the info he wants. Despite this, L genuinely wants justice to be served, and considers Kira, in killing criminals (as well as other innocent people later, such as FBI agent Raye Penber and his girlfriend Naomi Misora) to be equally wrong and just as evil as them, and that he should be punished for his crimes.

Abilities

 * Genius-Level Intelligence: L's abilities lay mainly in his skills of deduction and his intellect. An exceptionally intelligent individual with a great amount of enigma, L is quite possibly one of the most intelligent people alive and proved to be clever enough to match Light Yagami. He is incredibly observant, noticing the tiniest details, that most would not pay attention to. His mind also processes information quickly, giving him an accelerated learning aptitude. He possesses an eidetic memory (he never forgets anything and has perfect instant recall), he can read at superhuman speeds, and can intuitively understand what's going to happen and how to deal with it.
 * Master Detective: Due to him being extremely observant and cunning, he can easily find out how and what has actually happened, mostly by using logic. L notices the rapid rate of criminals dying of heart attacks, and suspects a person is behind this and that he is in Japan. Not long after this, because of the time of day during which the criminals die coincide with out-of-school hours, he deduces that Kira may well be a student. Not long after this incident, criminals begin dying during one-hour intervals, intentionally contradicting L's theory, showing to L that Kira has access to police information. L finds footage of the death of one of the agents, and the footage shows that Raye Penber, who was investigating the families of Soichiro Yagami and Koreyoshi Kitamura, was reaching for something behind him when he died just outside the train. Furthermore, the body of Naomi Misora, who previously worked with L on the Los Angeles BB Serial Murder Cases and was Raye's fiancé, went missing. L assumes this was the work of Kira because Naomi didn't seem like the type to commit suicide at the loss of her fiancé. Because of these two factors, Kira must be among those whom Raye was investigating.
 * Master Tactician: His advanced intellect allows her to perform various acts and set up traps in places, based on his accurate predictions. He shows this by using a death row inmate Lind L. Tailor introduce himself on television as "L" and say that Kira is "evil." This provokes Kira into killing Tailor on the spot, which in turn confirms that the Kira killings are not a coincidental succession of heart attacks amongst criminals but the designs of an ingenious murderer who will kill any and all who try to stop him. It also reveals Kira's location, since the broadcast was televised only in the Kanto region. L's strategical aptitude can make him extremely unpredictable, as he displayed the willingness to go at great costs to carry out any complex and dangerous plan he had thought upon and he even seemed to always think many steps ahead and form backup plans in case his original plan failed, as evidenced when attempting to raise a successor to L, Near and Mello attempt to catch Kira, with Near doing this in order to avenge L and defend his pride.
 * Polymath: He is incredibly knowledgeable about various scientific concepts, chemical concepts and other academical prospects.
 * Expert Deceiver: L displayed considerable skill as a con artist, even able to steal Misa Amane’s phone from her without the highly perceptive Light suspecting it.
 * Multilingual: L is fluent in English, Spanish, Mandarin, Japanese, Russian and various others.
 * Accelerated Metabolism: L suggests that even though he eats only sweet foods, he remains underweight because the brain uses the most calories of any organ in the body.
 * Master Martial Artist: He is also shown to be very proficient in many known martial arts and boxing and had an aggressive, if not slippery, fighting style. His style also involves psychological warfare. He is a very adept boxer and was able to hold his own, overwhelm and defeat opponents much larger than himself, or multiple opponents. However L is not above cheating, and will often use the environment, and other distractions in order to gain the upper hand when outnumbered, or outsized.
 * Skilled Marksman: Though not as skilled as Watari, he is also a proficient marksman.