Questions & Mysteries Kaido placed Shanks on his top 5 despite only fighting him once on his way to Marineford or...?

[Cruxroux]

They only clashed once and Shanks must've flexed on him.

" I have a bigger CoC than King of beast , now leave or I'll be exposed as fraud "

 

[Warchief Sanji D Goat]

Indeed.
The opinion of the stupid fish Crydo of 100 Hostages doesn't matter.

 

[Kiiro]

Well, it might have been a small clash but with full power.

Kaido acknowledges haki as the greatest power. So all Shanks had to do wad display his full haki abilities so prove him he is a strong fool. No need to have an extreme diff battle when Kaido can sense his power.