Amylin
SephirothJr0
Leirel
Nither are truly bad because due to different reasons both went insane, and an insane percon has no controle of their actions.
I'm going to have to disagree. Yes, I can belive Dyne went insane. However, Sephiroth spent many years study'n and finding out just who he is. Also, Sephiroth takes time in planning out his next moves and is constantly reminding himself of his motive and goal. These aren't the actions a clinically insane person would take. I know from experiance that someone in such a state of mentality acts on instinct and never looks at things from heinsight.
So did Hannibal Lector... I feel Sephiroth is worse than Dyne. Ever of hot and cold crimes? Hot crimes are crimes done under passion; they're typically unplanned. The kind of crimes that Dyne committed... he did not take the time to rationalize his actions. While his reasons may not be as big as Sephiroth's his lack of consideration for his actions becomes evident in his suicide.
Now, Sephiroth... as you said took time, a great deal of it, and considered his actions and planned his every move. Sephiroth committed what would be considered cold crimes. He was not driven by a blinding passion like Dyne. He took that time to consider what was the best move that Dyne didn't and still decided to continue.
You could also consider it like this... Hypothedical situation...
Dyne crimes: This could be considered as like this... say Dyne had been happily married for years. He suddenly walks in on his wife and the man she was having an affair with and in the heat of the moment grabbed his gun and shots them both without thinking just angry.
Sephiroth's crimes: Now, in a similiar situation, Sephiroth discovers some things aren't right and realizes that not only is his wife cheating on him but they were stealing money from him and trying to socially/politically ruin him. Now, they don't know he knows and he has time to consider his options and instead of turning them over to the police or, something along those lines, he still plans how he going to kill the two.
I hope you guys understand that.
So that's why Dyne was considered mislead psycho while Sephiroth was considered a cold-blooded murder. But Sephiroth being so "evil" is what makes him such a great villian.
You're good

