when you supposed to have at least better physical strength /AP than Kata because you're an ancient zoan yet you failed to damage Sanji even though u used your strongest mode (physically)
Can't bypass RS dura while casual Kata makes Ichiji bleed and unconscious.
And of course King wouldn't kill Sanji lmfao. But it was clearly not him running away. His honour was on the line and Luffy's simply the bigger threat, so of course he went to stop him. Also, King's gonna fight Marco anyway. There is no better opponent for him this arc.
He grabbed Sanji's neck when Sanji was grabbing Momonosuke. And when Sanji threw Momonosuke King used his full zoan form. This is same situation whan Sanji had to grab Luffy and had to face BM pirates to protect Luffy lol. Sanji can't go all out otherwise he would injure Momonosuke. Sanji also hasn't used DJ.