if you were the writer what you would have changed?
i am curious to know different theories 

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 -_- 

JDT should've been the real killer of MSA, I always felt OYH being the one who did it was too predictable. But I guess OYH getting killed like that was karma for her. SSR should've stayed alive in the ending, and what was the point of reviving Logan if he was just going to die again in the end?

@sunset
i agree wit you about MSA, it could have been a good twist, like OYH thought she is the one who did it and then i don't know like SSR was trying to kill her and at the last moment they discovered that it was JDT.
about Logan i agree with you too!!