Disclaimer: I don't own Death Note
Light Yagami had always been the very epitome of perfection and beauty. He knew that he was the centre of envy for many people, even those who had only been in his presence for a few minutes fell under a hypnotic trance, unable to acknowledge anything other than his flawlessness. He had a countless amount of friends, whom hung onto every word that came out of his mouth, as if they were spoken by God himself. Even his family believed his intelligence to be immeasurable, and they subconsciously accepted his superiority. He was an idol to many, looked up to even by experienced police officers and teachers. He seems to commandeer respect, and he always got it. People knew that if they ever went against Light in any way, shape, or form, it would blow up in their faces. This bored Light. Having nobody to match his intelligence proved to be incredibly dull. He secretly yearned for a challenge that would require him to test his mind to the limit. However, he though this would forever remain a fantasy.
That is, until he met L.
L Lawliet had known his mind worked differently since he was a young child. He was able to instantaneously solve complex equations that took normal people hours to solve. He found patterns in data that no ordinary human would ever be able to recognise. Even when he was put into an orphanage specifically for intellectually gifted children, his I.Q was still high above theirs. Within a week of his being there, he had shot to the top of their ranks, getting higher marks on tests than any previous students had ever scored. People regarded his intelligence with a detached sense of awe, similar to how one would regard a supernatural being -with the knowledge that no matter how hard they tried, they would never be able to match them. L had never once met someone who even came close to his level of intelligence.
That is, until he met Light Yagami.
When L and Light saw each other for the first time, both of them instantly knew that they matched each other perfectly. They received the exact same scores on exams, they both came to the same conclusions, and they both held the same air of superiority over others. They were so perfectly matched in intelligence, that it seemed they could read each other's minds. It was obvious from the beginning that they would never be able to remain neutral toward each other. They would either become extremely close to each other, or become enemies. Unfortunately, the latter turned out to be the case.
The next year was exciting for both L and Light. For once in their lives, they had a worthy competitor. They had to use their minds and push themselves to their intellectual limit. Both were always entertained, and never ceased in coming up with new plans to kill (in Light's case) or capture (in L's case) their opponent. It was a completely new experience, that was thrilling for both of them. L knew that it was morally wrong, but he was happy that the Kira case was taking so long to solve. He was confident he would win in the end, but for now, he was enjoying the competition. If the Kira case had been like all the other cases he'd taken on, it would've been finished within a week, and L would be back to his ordinary, monotonous life of figuring out cases deemed impossible to solve within a few days. But it had been months, and L still hadn't found the evidence he needed to convict the culprit -the only evidence he had at that moment was circumstantial, and would've been dismissed by the court immediately.
He was almost completely certain that Light Yagami was the culprit. It was only a matter of time before Light would slip up, because surely, he would have to make a mistake at some point. He felt rather melancholy at the prospect of the contest ending, but he was sure that the look on Light's face when he realised he had been caught would be worth it.
Little did he know, L would never be able to witness this.
But still, even though L and Light were matching in Intellect, Light had always had an unfair advantage.
By the time Light had regained his memories, L knew about the existence of the Death Note. But, little did L know, Light had one final trick up his sleeve. It was the fatal, deciding blow in their metaphorical boxing match. Light had a shinigami on his side.
It is obvious that no matter how well matched two people are, if one person cheats, they would beat the other easily. That is exactly how Light won his battle with L. He had an unknown ally, one that would never be called under suspicion. L thought nothing of it when Rem disappeared from the investigation room. He was unaware that, as he continued to investigate Kira, his execution was being organised.
When the screen went blank, L was confused for the first time in his life. When he felt a strange pain in his heart, L felt scared for the first time in his life. When Light looked over him, a smirk on his face, L knew that he had been beaten for the first time in his life.
Because he knew that, even though Light cheated, he still emerged the victor. He knew that Light had won the battle, even though his methods were unfair, and impossible to predict.
Because no matter how unfair it is, a cheater always wins.