Shanks has King's Haki, his clash with the Half Giant WhiteBeard (I says Half Giant coz he is a Giant to the average man, but OP has Giants much taller than WB). The clash causes a cut in the clouds, we all know that clouds are really up in the air.
Shanks rival is Mihawk who slices icebergs the side of mountains clean with the wind from his blade and does the same with pirate ships.
Anime Vice does allow users to bump old threads. Please bump old threads that have a fair match up and follows our rules. Since Shanks has not revealed enough feats, a discussion cannot be carried out properly.