What is unique about Islam is prophetProphet Muhammad Peace be upon him.
He sat out examples that no prophet has ever done before. He did not have any miracles as other prophets used to have, he did not have any miraculous powers yet he accomplished everything with any special privilege from God. He was thus the most beloved prophet of God.
He was stoned severely by the people of Taif when he was giving them the message of Islam. When God saw his beloved prophet is bleeding from stones because he was propagating his message, he immediately sent Angel Jabriel to help. Jabrial asked the prophet, if you want I can crush the people of Taif between the two moutons (this place was valley between the two moutons). The prophet said no, they are ignorant, they do not know who I am. Most Muslims believe any other prophet in the situation would have order this punishment, as was in the case of Noah and other prophets, but Muhammad forgave them. He choose love instead of hate.
Prophet Muhammad peace be upon him was not given any special power to assist in spreading Islam. For example Moses could divide the sea in two and his stick could change in serpent. Jesus christ could heal any one who was near death. He would even make a dead person alive. Suleiman could understand the language of all animals and everything was under his command. He would order a bird and that bird would obey his order. Prophet Muhammad was not given any special power yes he preach Islam like other prophet did in the past.
Prophet Muhammad was given the complete code of life. No other prophet was given this privilage.
The justice that Prophet Muhammad peace be upon him preached was unmatched by any other prophet in the past. He made himself subject to any punishment that his follower were subjected too. Towards the completion of the Dean (Islam), once the prophet addressed a crowd and said is there anyone to whom I owe anything? No one came up except one Sahabi. He said, oh the prophet in one of the battle I was hit by one of your arrow near the side of the gut. The prophet exposed his gut and said you can hit me too. In other words, his justice was unmatched by any prophet. He was fully accountable by all islamicIslamic rules that he preached himself and he did not deviate.
He by far exceeded the goodness of any man who can possibly exist.
{noteNote I need to clarify my last para more. Did some research but did not find relevant info}