With the recent revelation in volume “4 Billion” that came out with Film Red, we learn that Shanks has a title known as “Killer of Observation Haki”. Apparently, Shanks has this title because he has an ability known as “Sign of Presence”, which allows him to disrupt his opponent’s use of future sight by concealing his own presence.
I believe Oda has foreshadowed this ability in Episode 869 when Rayleigh was training Luffy. Rayleigh mentioned that he had completely concealed his presence when going for the 100th strike on Luffy.
Funny enough, Rayleigh mentioned Luffy seems to have a knack to feel other people’s emotion with his Observation Haki, so this might be a great counter to Shanks’ ability.