"Which is highest power of this universe ?"
I see a lot of focus on gravity due to it's vast influence but does that also mean it is the "highest". I don't consider the blood in my body to be the highest power in my body; despite the fact that it is essential to the healthy function of every part of my being. I consider the cognitive abilities of my mind the highest power. And when considering these powers and it numerous functions I do not consider the subconscious functions nor the entire nervous system to be the included in that "Highest". The highest would be that part of higher thought which provides to me self awareness, reason, logic, and the ability to reconcile it all with the passions of my heart. This is probably physically speaking a small part of my being, but clearly the highest power I possess.
I would have to say that anything, no matter how small or finite, that possess self awareness is on a higher level than something which does not. And something that posses the higher intellect giving way to reason, despite its fragile nature, is even higher so. Than anything with an emotional development matching this higher reason, is even higher. And that anything with the the ability to reconcile this developed emotional self and intellectual self with each other is yet higher.
I venture to suggest that with this ability to process thought on this higher intellectual level married with the passions of a developed emotional self, that we start to breach the possibility to influence the flow of cause and effect. I suggest the possibility that there exist a state in which an entity can weaken the bonds of cause and effect and take for itself a small measure of freedom. If such a state did exist then I think that this would be the highest power in the universe. And as of yet, Humans are the closest known entity to this position. While we are still slaves our-self, we do flirt with the edge of gaining a small portion of power. Yet an entity with no intellectual thought or the ability of emotions is forever a slave to cause and effect.
I was also like to add that while it may move from entity to entity, that these cognitive abilities and emotional abilities are a constant factor in this universe. It would be very unlikely if humans were the first occurrence and it is very unlikely they will be the last. The entities that possess these abilities may be finite but as long as the universe continues to provide the right environment these type of entities are bound to happen.