You can say that about any story. That could also be said a murderer/r@pist in a story was messed up for drama. You can’t really blame the author for including a bad character.
Anyways from what I saw in the raws, the fiancé IS a bad guy. All the nice moments you see of him being nice was not the fiancé, it was the brother. Hence why I pointed out how to tell the difference between the two. The fiancé has literally also slept with other women, and also got one pregnant if I remember correctly. So no they didn’t mess up his character, he was like that from the beginning and his personality has always been trash.
At first I was gonna feel bad for the fiancé, but looking at the raws- DONT FEEL BAD. He’s trash. Also to differentiate which twin is which, looks like the ML has more wavy side parted hair, and the fiancé has more straight side parted hair. They also act completely different,