Kizaru "trying to kill Bonney"
Kizaru actually trying to kill people:
Whether or not Kizaru was holding back against Luffy is debatable.
Kizaru was definitely holding back against Bonney and Vegapunk. He let Bonney leave the island, and probably would have tried to save Vegapunk if Vegapunk had wanted it.
IMO Vegapunk was ready to die, then when Luffy showed up, thought "Oh... maybe this guy can actually change fate, and rescue me."
Once Saturn stabbed Vegapunk, is when Kizaru realized "oh, my friend is going to die... I'll honor his wishes."
Read this very intentionally:
Look at the bottom panels starting from the bottom right going to the panel where Kizaru stabs Vegapunk.
1st Panel: Vegapunk shots angrily for Sanji to leave him.
2nd Panel: Kizaru kicks Vegapunk out of Sanji's arms. Sanji seems mostly uninjured from this.
3rd Panel: Sanji reaction
4th Panel: Kizaru stabs Vegapunk with his light sword, Ama no Murakumo
So:
-Kizaru attacks Sanji directly from the front, rather than using beam attacks, and knocks Vegapunk out of Sanji's arms
-Sanji is unable to block Kizaru's direct attack
-AFTER Sanji is gone, Kizaru uses his sword to kill Vegapunk
-Rather than attack Sanji after, Kizaru waits, and lets Sanji pick Vegapunk up again and begin running
Kizaru was always on Vegapunk's side. Where did he kick Bonney down to? The Fabiophase, filled with... the Pacifista she can control, and away from himself, Cipher Pol, and the Seraphim. Kizaru knew Bonney + Pacifista could low-diff jobber Vice Admirals, he was always looking out for Bonney this arc.