While it may look like nothing more than a simple fistfight to the untrained eye, each one of them was actually imbuing each attack with an astronomical amount of destructive energy with each blow.
They were then strengthening their attacks with ambient cosmic energies, carefully manipulating the cosmic energy to not detonate the law of destruction's essence in their punches.
At the point of impact, they used the essence of the law of gravity to augment gravity in a way that increased the weight of their fists to make their punches deal more damage.
The duo occasionally tossed in the essence of the law of time to accelerate their movements in order to increase the speed of their attacks or increase their reaction speed to dodge.
For defence, they both coated their bodies with a thin layer of cosmic energy, one that was separate from the one that covered their fists and enhanced their attacks.
Your gift is the motivation for my creation. Give me more motivation!
Creation is hard, cheer me up!