Which animal has the most amount of available energy?

Hat you want to ask, is what level in the food chain has the most energy at their disposal. The answer then would be the group at the bottom of the food pyramid. They would be closest to the original solar energy that was trapped by plants. Thus herbivores ... those that feed on plants ... or those plankton feeders that feed on algae, should have collectively the most energy available to them.

As one goes "up" the food chain/pyramid, the initial energy of the sun because of the laws of thermodynamics and the "work" of animals, is transformed into heat which is unavailable for "work". Thus the top carnivores have the least pool of energy available to them and thus their populations tend to be small.