"Aramaki got heavily damaged by Momo"
"Shanks got Aramaki scared"
Aramaki, a one man army sitting there planning to take on the Straw hats and the whole of Wano, and there is another Emperor and his crew... and just then Aramaki leaves. You need 2 Emperors and their crews + other pirates to make an Admiral back off. No wonder Akainu went with 1 ship to capture Blackbeard and his crew. It's interesting that Aramaki immediately sensed/recognized Shanks and his crew, while Luffy didn't at 100%.