Well I don't care If he as his reasons or not or if her father was an incompetent ruler or anything. Like what the fuck? I completely understand why people hate Soo-woon. He fuckin killed Yona's father and destroyed her happy world. She loved her father so much - Why should we forgive and love someone who killed her father? Would you forgive someone that killed your father - "Because he has his reasons and because your father is an asshole?" Never. I would never.
Lol. I didn't say to forgive him. I'm implying that Soo-woon is one the great characters of this manga.
Though I could understand where the hate came from but it's actually usually too emotional. I guess it depends on each person.
Soo-woon grows in me. I hate him from the start but as I get to know him over the course of the story, I have love his characters as much as I have love Yona's.
It might sound like favoritism on my part for you who hate Soo-woon but he is indeed a great ruler that Kouka needs. It is already explicitly implied from the people who supports him to the overall situation of the kingdom

Guys, I think you need to chill out for a bit. You're hating Soo-woon too much. The mangaka had obvious laid out hints that Soo-woon killed Yona's father for a reason, whether it's good or bad. But one thing is for sure—King Il is an incompetent ruler.
You have to admit that aside from Yona, Soo-woon has a very interesting character development. Just open your eyes for a bit