I think Mihawk (worlds strongest swordsman) is stronger then shanks (worlds second strongest swordman perhaps?) , and shanks is stronger then admirals.
Fair enough, but where is the evidence to say he is stronger than Shanks?
They were rivals back then.
I believe Shanks with two arms was probably slightly stronger than Mihawk since Shanks is a Yonkou.
However, Shanks's strength doesn't come only from Sword Slashes. He has a monstrous Haki, and I think due to the fact that the same Akainu punch that put a hole through Ace, was the same punch Shanks effortlessly blocked when stopping the war, that Shanks has amongst the most monstrous Haki levels in the series.
Since Mihawk was being stalled by the likes of Vista, who is similar to Marco & Jozu and roughly skimming the Admiral tier level in strength, I doubt Mihawk is a world above the Admirals like you imply.
No, its impossible. If Mihawk couldn't "slaughter" Kizaru.
You're underestimating Rayleigh I believe. He's the First Mate of the most powerful crew in history. Old or young he'll kick ass.
You're also forgetting Kizaru's life wasn't in any danger at all when he fought Rayleigh.
Also, in One Piece, looking at the ages, characters are in their prime between their late 30s to their 50s.
ALL the strongest Marines are above the 35+ mark.
ALL the extremely strong characters who are amongst the strongest in the series are 30s+ in age.
(I'm not counting Luffy/Law/Kid since they are not amongst the strongest in the series)
Shanks is probably slightly stronger than the Admirals, and as a result, I can understand Mihawk being slightly stronger than the Admirals, I wouldn't be too surprised if you were right on that.
But for you to say "kill Admirals out of boredom", that's impossible.
Mihawk couldn't slaughter them.
Mihawk VS Any Admiral would make for an amazingly close fight.