So TVTropes has this wonderful little topic called "Fridge Horror." Among its wonderful entries is something from Mega Man, and it puts things scarily into perspective about Dr. Light's practices and the Three Laws of Robotics.
"The original series has Megaman vs. Dr Wily, with the latter never being executed for his actions. Eventually, Doctors Light and Wily make their final works, X and Zero, with Zero being imbued with the Zero Virus. The X series has the virus absorbed into Sigma, who becomes the new Big Bad and spreads the now Maverick virus. The virus is defeated, as seen in the Zero series, with Cyber Elves, but the source of said Elves is taken over by Dr. Weil, causing the Elf Wars that ravage the earth and kill off billions of humans and reploids, leading to the Zero series. After that, humanity and reploids merge into a single species seen in the ZX series. In the Megaman Legends series, it's revealed that humanity has been entirely replaced by Carbons, robots that perfectly mimic humans. The last human died before the series started. So, because Dr. Light was too idealistic to realize his little blue war machine should put down the Mad Scientist bent on world domination, earth gets fucked up and humanity dies off."
Remind me again why we put him in charge of saving the world?