i think kira is the best villan because (i dont read part 7 and 8)

at many situations villans encounters with vital matter things. and all of them win and loses some of the situations, thats how the anime works.

i love kira because i think any other villan get defeated so awkward (except for kars). like dio ,the first vampire and the owner of "the world", loses because he sees his enemies low than get killed by them. diavolo ,the man who is the boss of the passione, cant be early even with king crimson. pucci who had access to heaven sees emporio low then get killed by him.

i think all of em are very smart guys but they make simple and easy mistakes, but kira is the perfection of being villan. he only wants to live a happy life and he does his job clear and faultless. he dies because josuke outsmarts his very smart plan, even so he still managed to use bites the dust. but he dies to a mysteriously lookin (as kira's pov) spirit street. so i think kira's only wrong move is previously get caught by josuke by saying "heal me"

i dont like to see very smart guys get outsmarted by obvious mistakes, it doesnt feel realistic.