I'm not here to say that what he did was good but I'm here to say why it lead to that and why it makes sense.
"Sooyoung is inlove with him, he didnt have to do that."
True. What he did was stupid but it worked in the end, but still nonetheless stupid. That being said, Taesung actually regrets it as it almost killed Sooyung.
Now why did Taesung do this? Well being a gangster boss and someone who desperately doesn't want to lose Sooyung I think it's kinda not surprising for him to do this extreme measure. You see he wants Sooyung to stay and there were like two options:
1. Either force Sooyung to stay.
2. Or make Sooyung stay on his own accord.
Taesung is more than capable to do number 1 but why didn't he do it? Because he knows that it will only push Sooyung away or that Sooyung will hate it. That's why after hearing about his enemies coming for Sooyung, he saw an opportunity to do number 2. You see Sooyung is a tough and stubborn person. He doesn't really listen. He sometimes only listen when something happens. Hence why Taesung did this, he knows of Sooyung's stubbornness.
In the end tho, Taesung regretted this because he could've lost Sooyung forever. Which is why you kinda notice after that chapter, Taesung became even more possessive and overprotective of Sooyung, because he almost lost Sooyung once and he doesn't intend to let it happen again.
But I'll never forgive Taesung on that one chapter where he want to make sooyoung realize that he needs taesung and the only way for him to be happy is to be with Taesung. Sooyoung is inlove with him, he didnt have to do that. Poor Sooyoung, but i admire him. Sooyoung is so freaking tough and strong. Like there wont be any day that he will go home without having scratches. He did get more than how many times punches on his face and his head. Damn, we love you sooyoung