for me :
i would not kill OHY and i would have made all the 3 FL join forces to take down JDT.
i would have not make SEO JIN die in the end instead i will make her go crazy and went to a mental hospital.
i would have killed Logan from the start so that SSR would be more visous and full of revenge.
and for sure i would have not kill SSR it doesn't make sense at all how can she leave her only daughter alone -_-
and most importantly i would have not include ghosts in the story -_-