Shank is one of the few prominent characters beside Kaido, Gol D. Roger and Monkey D. Dragon whose abilities and powers are not fully revealed yet.
I think we can all agree that we haven’t seen enough of Shanks’ abilities. But, let’s see some examples of him demonstrating his powers:
When we first saw him with Luffy (in the first episode) and we see little of his fighting skills, mostly just his spirit, which he demonstrates againstand then to the Sea King where, he demonstrates .
Then after 10 years, with only one arm left, he is been visited byon an island. We all know Mihawk is the best swordsman in the One Piece world. After we learn that they’ve had regular matches with one another, which means in terms of powers he has to be very strong to be a match for Mihawk. Also then he demonstrates that he can take a blow from the . And when he entered the Whitebeard’s ship his haki not only knocked out a lot of , but also damaged the ship. Also this caused ‘s scar to ache and have and commend about his spirit.
Also before the Summmit War Arc he was fighting another Yonko, which according to Law, is “the strongest creature in the world”.
After that events, we saw him in Summit War Arc where he stoppedwith .
Also It’s not just Shanks that’s strong, his crew members are strong too,was able to make Kizaru stop for a moment during the Summit War Arc.
Challenged everyone after the war: the three Admirals, the Fleet Admiral, overshadowed old school player Garp, Blackbeard (who had the strongest Logia and strongest Paramecia), but yet no one stepped forward!
*Theory by Nilesh Jha