upper hand
whip hand

It would give him the whip hand when they met in two days time.

"It's too early to say he has the whip hand."

Ruark did not like to be ignored, especially when he had the whip hand.

If they found her, Bugsy would hold the whip hand from that moment on.

Once we're in the Sol system with this force, we'll have the whip hand.

That kind of man could be pushed a ways if he thought you held the whip hand.

Nutrition has begun to have a whip hand over breakfast.

It's only when you've got the whip hand can you demand something.

Everyone wants to be there, so the Chinese have the whip hand.

Their assumption from the beginning has been that they held the whip hand.