What I love about One Piece is that it isn't strict power levels. Some abilities do better against others, and some overpowered abilities are given to people who don't abuse them. Mr. 3 stood a better change against Magellan than Luffy because of his fruit. Was he stronger than Luffy or Magellan? No, however his ability gave him a better shot at survival.
On the topic of Kizaru, remember during the war when he sniped the key to Ace's cuffs? That could have been Luffy or Ace's head. Kizaru is "gray-area justice". If it was Akainu, he would have sniped both of them in the head. If it was Aokiji, probably a shot at the platform to simply knock Luffy off of it. However Kizaru took that middle chance, he shot at the key, leaving Ace still stuck, Luffy still having a chance, and Sengoku having the opportunity to kill them.
Does Kizaru have an overpowered ability? Hell yes. Is he at the very top tier as far as characters go? Not at the very top because it's not in his personality.