there NOTHING I wish more than that bitch Ryokugyu face Shanks in a 1 Vs 1
But even then 2 whole Yonko + their crews were about to lose to Aramaki so Shanks may need to broker an alliance with Luffy and Buggy just to be sure he can take one Admiral.
He made Akainu (Aramaki's idol) cry and the Marine HQ submit to his demands.
There are not enough ships in the OP world to make Shanks brave enough to actually fight Navy HQ given the fact that Shanks brought 500 ships and Elbaf to face Kid lmfao. If Sengoku agreed to a fight, Shanks would’ve probably just used all his might to help the Whitebeard Pirates run away.