YQ is a dark character. I am only stating the facts :
Did he collude with Murong Xuan Lie, even though he knew that shu Muo's death was linked to Murong Xuan Lie? Yes, he did.,
Did he used the henchmen of Murong Xuan Lie to frame Murong Jing He for murdering 10 beauties ? Yes, he did.
Did he try to hide it from Mei Lin hoping that he could manipulate her in hating her beloved Prince Jing, because he wanted to still her love?
Yes, he did.
Did he try to make Mei Lin feel in debt with him from the very begining, offering her ( several times) the assistance of his henchmen to help her in her revenge. For the sole purpose of manipulating her into keeping the interaction with him?
Yes, he did.
(This is why Prince Jing did not want her to make any promises to YQ. And he said that he would repay YQ's favor in her stead.)
Did he try to force Mei Lin into marrying him, by negociating a "trade agreement" with the Emperor of great Yan, whereas he was colluding with the Xiyan's Priest to fake the Crown Prince election ceremony?
Yes he did.
(Again, he sole purpose was to take Mei Lin with him. He had to make her feel in debt with him for saving her life. Meanwhile, she had to come with YQ in Xiyan to avoid his father killing attempt. If the latter did'nt believe that YQ was the real reincarnetion of sun kunlun, YQ would have been killed by his own father long ago.)
Now Mei Lin and Yue Qin are in Xiyan.
The guy knows that Mei Lin is still completely in love with Murong Jing He.
What does he do :
First, he is following her everywhere she goes and he also asked his henchmen to do the same.
Secondly, he asked MRJH to never see her again ( let go of her) at the memorial ground.
(wich is weird, because MRJH is the governer of the city, his position might lead him to see her again)
Thirdly, he he harmed several maids, in the process of looking for a way to keep Mei Lin, knowing that she would never permit this kind of atrocities to take place because of her. Obviously, he knows it as well. So he chose to hide his crime (as usual) and lied to Mei Lin about her recovery.
Forthly, Mei Lin has discovered his crime. What is YQ's great idea???
Lock her up and harming her to suppress her martial arts skills and thus not keeping his promise of giving her freedom of choice.
To conclude YQ was always a dark character, who conceiled his misdeeds from the very begining. And only now, Mei Lin can see his real face.