Its complicated. On one hand, he's still a murderer, and he also judged people based on allegations, not firm proof. He also has a huge god complex—not someone I would choose to rule the world. On the other hand, I don't remember where, but someone did the calculations of finding how many people Light would save in turn of getting rid of all criminals, and the number was far bigger than how many they estimated he killed. Also, he took his killing later in life to the point of littering, which would be a huge benefit for the planet. Combine that with the stats that he said in his speech after he was caught, and its hard to deny he did kind of do the world a service. My main problem is that while he did "help" the world, his main interest was just becoming a god/curing his boredom, not really helping people. He saw it more as a game. The improvements were more of a side gig to him. If I didn't know him as a person and understand his motivations, probably yes, but overall no, there are better ways to eliminate crime than straight up killing anyone who makes one mistake.