Responses
I don't think some people realize that MC was given a love potion as well. Besides that sure, there is a reason behind his actions but It doesn't erase the things that were done and the terrible things MC went through because of his actions. It doesn't matter If he wasn't or was under the influence of love potion. Mc will never be able to forgive him and It's simply a human reaction. It's not possible for any sane human being to forgive him in the place of MC
Spoiler
MC's fiancée is another pitiful character and there's a reason a lot of Korean fans wanted him as an ML. He really loves and adores MC and since childhood he wanted to be her knight and marry her. In the first timeline, Angela used the love potion on him and no one is immune to the love potion, only the one who is blessed by the dragon god. So everything that happened in the first timeline was because of the love potion, but that doesn't change for MC because even if Carsel is different in the second timeline, she has already experienced everything in the first timeline and is hurt and traumatized.
In the second timeline, Angela didn't use the love potion on Carsel because MC had told her about the second prince, who was the crown prince at that moment, so Angela thought, why should she choose MC's fiancée when there is a better choice. In fact, Carsel and Dan and the second prince are the only three men in the story who feel nothing for Angela or her beauty. Carsel and Dan didn't care for her because they loved MC, and the second prince just because he likes women with voluminous bodies and Angela didn't had a voluminous body. Later on, Angela will use a love potion on the second prince, just like in the first timeline, because it's the only way for her to get him, but that's another story.
The reason a lot of people like Carsel is because he's an innocent character who really loves MC and would do anything to make her happy. Once he was going to a ball with her and asked MC what her favorite color was, and I think MC said blue, but I can't remember it well, but Carsel ended up wearing all of the clothes in that color that day just to see her happy. Since childhood, he also learned to fight the sword in an elegant way for MC, although fighting like that was not really effective.
He realizes that MC is distancing herself from him but he is still trying and MC also realized that Carsel was under the influence of the love potion in the first timeline, so the second timeline Carsel is really innocent, but she is still traumatized and hates Angela for doing this in the first timeline because now there is a rift in her relationship with Carsel and not only is she hurt by it, Carsel is too.
After some events, her and Carsel's engagement is broken up due to political problems and Carsel is devastated and visited MC at night to speak to her, but MC tells him that there is nothing they can do about it and that they cannot return. Carsel understands this and gives her a knight oath and told her that he will always be her knight and protect her.
When MC is attacked by assassins ordered by the third queen, MC was rescued by an unknown man who fought the assassins with her guards and then simply disappeared. MC realized that the unknown man was Carsel, who apparently was always around, and protected her from the dark. On another occasion, MC was in an underground prison and Carsel came to rescue her in his uniform, but after MC saw Carsel like that, she backed away and yelled at him not to touch her because she remembered the first life and confused Carsel with the Carsel from the first life. Carsel was hurt and confused, but he thought that maybe she didn't want him touching her because she was shocked.
When MC married Dan, Carsel was hurt and realized that he has no chance anymore, but still wished MC the best and to be happy. In the end, Carsel wants to look ahead and after passing the knight test, he decided to join an order of knights that he liked and not be MC's guard. MC is happy that Carsel wants to look ahead and start a new life for himself.