Winter never intended to kill Huang An. All of his actions were only intended to intimidate Huang An. After all, Lin Yuan had never given him any orders to deal with Huang An.
Winter attacked and injured Huang An because he knew very well that a fellow like Huang An would only submit if he injured him and made him truly feel the threat of death.
Compared to Lin Yuan taking the initiative to invite Huang An into Sky City, it was better for him to use these unconventional methods to force Huang An to submit. Otherwise, even if he intimidated Huang An now, he would definitely put on airs again when Lin Yuan invited him.
"Whether or not to spare your life depends on our Young Master's decision. Our Young Master will meet other Creators later. Seeing you was just a spur-of-the-moment idea."