Revelation 17:8 is a reference to Revelation 13:3. The head that was wounded isn't a person, it's a kingdom. It's the 7th head. Which is called in other passages of the book "the beast" (with the ten horns). The 7th Kingdom didn't exist before the 6th, it existed after, but was wounded, that means it lost his power and splited into at least 10 Nations, which are the 10 horns.
The Roman Empire cannot be the 7th head because it is the 6th. The 6th head belongs to a completely different beast/material, namely the leopard/bronze (3rd beast). The 7th head is the head of the 4th beast, so it is a completely different beast/material, with a completely different culture and language. The 3rd beast with the 4 heads was Macedonian, Ptolemaic, Seleucid and Roman. All 4 shared the same language and almost the same culture.
To find out who the 7th head is, we need to consider the 2 requirements it must have to be a head.
1. it must have destroyed the previous beast. The 1st beast was destroyed by the 2nd beast, the 2nd beast was destroyed by the 3rd beast. So the 4th beast must have destroyed the 3rd beast.
2. it must have conquered Israel. All six heads conquered Israel and that means the 7th kingdom must have done so.
With these 2 requirements, only 2 candidates remain. The Rashidun or Turkish Empire. The Rashidun Empire didn't destroy Roman Empire but it was the Empire that conquered Israel after the Romans. Turkish Empire conquered Israel and it destroyed the Roman Empire in 1453.
Both of these empires have fallen in the past, and both of these empires have divided into at least 10 nations. That means that one of these two empires will return.