When I wrote my last thread I was wondering if Vander Decken the 1st or Davy Jones could have been the first guy to touch the forbidden sun/the creators of DFs but at that time I ruled that they weren't from that era... I should have gone with Davy Jones.
I think Imu is 4th last battle, at best.

Imo, the order is like this Imu>Blackbeard>Buggy>Davy Jones.
And if Buggy and Teach are both Rocks' sons, we might add Man with burn scar as 3rd Rocks' son as another obstacle which would make Imu 5th last battle...