I think the man marked by flames is Edward Weevil.
When the man marked by flames is first mentioned it pans in on Law which seem to indicate he knows who this person is. We know that Law is famous for being the mastermind behind the Rocky Port Incident. I think it is related to that event.
We now know that the Rocky Port Incident was Law stealing those 100 pirates he gave to the World Government to become a Warlord from Hachinosu.
Koby also became famous for that incident for saving civilian lives. Koby does not like to take credit for it. But I find this info suspect because would Law really risk the safety of innocent people.
Another interesting tidbit is that Blackbeard credits Koby for him being able to topple Wang Zhi and taking over Pirate Island. Which is weird because you would think it would be Law. The suggestion seems to be he fought Ochoku and/or his men. Also I questioned if Law would really attack an island run by a legendary pirate alone.
Then I remember some interesting dialogue from Law in Wano about pirates doing nice things for people making him sick. Did he himself do this in the past?
It is also revealed that the damage done at Rocky Port was so extensive that it was recently repaired. Again this doesn't seem like Law's M.O.
We do know a pirate who causes mass civilian casualties and destruction. Edward Weevil.
There seems like there are parallels between the God Valley Incident and Rocky Port Incident. I think Weevil attacked Rocky Port and Koby went their to stop the destruction. He teamed up with Law and they both saved civilian lives. Law took the opportunity to steal a 100 pirate hearts to become a Warlord. I think Weevil was responsible for weakening Wang Zhi allowing Blackbeard to dethrone him. Which is the reason similar to Garp, Koby dislikes taking credit for it.
The big question that pops is why would Weevil's involvement be unknown. I have another tinfoil hat theory that might explain why.
