Finishing up a role was always a hard thing to do for actors. Especially, when it was an intense role.
If you are too immersed into a role, then you feel like you are that person and it is hard to differentiate between your real personality and the role.
That had happened with Aiden when he played the role of Flynn Wheeler in [Sherlock of the Shadows]. It had a lot to do with him turning off security protocols that helped him stay sane during immersion.
But it was true that the role was intense.
Same was with Kai. Probably more so because Aiden felt much more close to him than any of his characters.
When he was doing the final scene, the only thing in his mind was that it was going to be the end of Kai and for a while, he even wondered if he would be able to remove Kai from his mind.
The answer was obviously no.