L Lawliet is a genius detective who possesses extraordinary intelligence making him stand out from normal humans. He is a silent, amoral, and intelligent person who is known for his effective skills such as social influence, stealth mastery, and weapon mastery. He is also an extremely good tennis player and proficient in capoeira. On the other hand, Kira or Light Yagami may have a highly-esteemed IQ level of 215 but he is a mere mortal genius having a God complex with an inflated ego and composed personality. Kira's physical prowess is that of a peak human which is not on par with the skills L Lawliet possesses. Kira is secretive about his Death Note, which is his main arsenal, while L Lawliet is known for his efficiency and cunning. In a scenario where L Lawliet is assigned to solve Kira's case, he would have the upper hand. With his extraordinary intellect and detective-like skills, L Lawliet would be able to deduce Kira's identity and master plan. L Lawliet would find a way to counter Kira's strategic moves and manipulation tactics. In conclusion, L Lawliet is the winner of this battle, as he has a range of skills and expertise to outsmart Kira's divine-like ego and manipulative tendencies.