That's why it's more make sense for Kaguya to be relative to Isshiki. Because the 10% points is inconsistent. It will be make more sense for Kaguya to be able to harm him. If we use the logic that Isshiki is ten times stronger and faster, the reaction will get harder too. When you punch something, you will get an equal reaction of energy of your punch, as dictated by Newton's third law of motion, which states that for every action, there is an equal and opposite reaction.
When you punch an object, you are exerting a force on that object, which in turn exerts an equal force back on your hand. This force is what we feel as the impact of the punch. The amount of force that is exerted on your hand is equal to the amount of force that you exert on the object being punched, as the two forces are always equal and opposite.
Additionally, the amount of energy that is transferred during the punch is also equal and opposite, as energy is a scalar quantity that is proportional to the force applied and the distance over which that force is applied. This means that the energy of your punch is transferred to the object being punched, but an equal amount of energy is also transferred back to your hand, resulting in the impact that you feel.
Therefore, when you punch something, you will always get an equal reaction of energy of your punch, as dictated by the fundamental laws of physics. This is why it is important to consider the force and energy involved in any physical interaction, as they are always equal and opposite, and can have significant consequences for both the object being acted upon and the object doing the acting.