Here’s the question:
Unusual, even surprising question, yet I understand why someone would ask about it.
I think everyone who have read the manga or watched the anime and the live action movies (and recent drama) already knew that Light Yagami murdered L using the death note. With that singular act alone, I would say Light is evil, but he’s not pure evil (at least not yet). One needs to understand the radical change in his persona to make a proper judgment.
Before he discovered (or was selected to ‘own’) the death note, he was a young man of ideals. He is intelligent, hard-working, and even considerate. He came from a family that values loyalty, the law, and justice. His father is a police officer, and he is aware of what sort of law enforcer his dad is for years. However, the circumstances with his family and the values they nurtured was sidelined by the death note. The power to kill anyone, plus the prodding from the shinigami have corrupted Light. This corruption has changed him from a thoughtful, law-abiding citizen into an evil, arrogant god-like creature with grand designs for the world.
His decision to kill anyone that would block his way towards realizing his ultimate goal – that of ridding the world of murderers – made him a young man of evil. That complete his turnaround. How do you justify the means to an end? You don’t.
This is our third post for the new Q and A section featuring selected Quora questions that I have answered.
[ I reviewed the Death Note drama previously, you can read them too for some more perspective ]
On the other hand, L Lawliet may appear to have a bubbly (weird even) yet mysterious personality, who would not allow himself exposed to the world. This insomniac, who loves to walk barefoot, is said to the greatest detective the world has ever known.
The most I would consider him as “evil” is when he utilized invasive investigative procedures. Well, that is not even “evil” from the perspective of the investigator (or the police) since certain techniques are used to get information and arrive at the truth.
I also think of L as being a lonely young guy who just wants to connect to someone and gain a friend. He thought Light might be that friend and while he is already aware that Light is also Kira, he still held on to the notion that Light might be persuaded to change his ways.
Of course, that did not happen, and he was murdered in cold blood. So much for friendship and loyalty and trust. Light was quoted once as saying:
I can’t develop feelings. That’s how most idiots screw up.