@Abiss
Spoiler!
From here on in the story, he's no longer a distinct "enemy" and as the story continues, he genuinely desires to be an ally of Rimuru. You'll later find out more regarding the "why" he thought he had to fight and kill Rimuru. It's pretty pathetic and it's mostly due to him being such a high level genius IQ that he's fully lost himself up his own a**.
Like most characters in this story, the defeated either join Rimuru's side or they are killed off. You can consider this moment to be Yuki's "defeat".
Like most characters in this story, the defeated either join Rimuru's side or they are killed off. You can consider this moment to be Yuki's "defeat".