KravenMorehead™
Barrel Brothers.®
you're confusing the comics with the MCU...simply being in possession of the stone increases strength, durability and stamina.
even if he did not consciously evoke the the Power Stone, Thanos was still augmented by it and gave him the edge he needed over the Hulk.
i agree that Thanos may posses the power to defeat a version of Hulk that is not enraged enough to defeat him but Hulk got his shyt handed to him in a way that i believe the Power Stone must have been involved.