I believe Peter the Great, Frederick the Great , Joseph II, and Catherine the Great were all very enlightened despots because they were distictively different from other monarchs of the time period. They ruled their subjects using the principles of the enlightenment. This meant that they ruled with the purpose of developing their subjects, for their well-being, not to please the nobility. They still believed they had the right to govern by birth, but what they did with their power was what was different.
Peter the Great was credited for westernizing Russia. He did many things while in power including aboloshing the serf system which tied tenant farmers to certain properties for life and replaced the powers belonging to the nobility with a greatly expanded bureaucracy composed of educated civil servants. This was obviously a decision made for the people. Peter undertook many extensive reforms uncluding centralizing the government, creating a regular army and navy, took control of church property, making it fully linked to the state, abolishing church heirarchy.
All these reforms were in favor of the people. These were enlightened decisions. Therefore Peter was one of the enlightened despots.
Fredrick the Great devoted himself to making Prussia stong. In doing so he wanted to geographically expand their territory. So he invaded the Austrian province of Silesia, and was successful in doing so. Fredrick was considered a military genius and also established Prussia as a great military power. He financed the rebuilding of towns, and roads to better travel. Besides his military success Frederick also established universal religious toleration and granted freedom of the press. He established protections for the people against the law, by speeding up the legal process, and aboloshing torture. These decisions were with the people in mind, making Frederick also a very influencial enlightened despot.