I like King for a few reasons.
First of all, his competence. Whilest everyone is out of their minds, including King's captain who is sweating buckets, King casually flies over, reminder that King's captain also possesses a devil fruit that enables flight, and takes care of the threat, whilst being cocky about it, calling it a measly ship, completely humiliating an entire Yonko crew and stopping a full-scale war.
When King's captain is in a pinch about Yamato it is King who has preemptively sought out a solution to the problem, acting like a true right hand man.
When the people try to free Momo it is King that acts immediately, first flinging Shinobu mercilessly into the building, then playing with Sanji.
Secondly his design. It's one of the best I've seen in OP. Straight up scary and intimidating. The mystery behind his race. Are the wings part of it, or something else? His entire menacing aura and badass vibe.
His cockyness.
Calling a Yonko crew with a Yonko on board one measly ship
Bullying Jack and trash talking Queen
Staring Linlin down in a cold way and completely rejecting her offer
Trashtalking the F6 and putting them in their place
Accepting the chance of a fight with them without any second thoughts, being completely sure of crushing them
Trashtalking Queen in the latest chapter
Taunting Sanji
I am a sucker for flex moments done right, and badass dudes. And there's still left to learn about King.
At the end of the day I dislike this type of discussions since everyone has their own reasons for liking or not liking a character, and their preferences towards some. Since I don't really enjoy discussing tastes and I believe they shouldn't be discussed, I'll leave it at this.