Well he'd be above King as far as the hierarchy of the crew/strength.
People act like the entire country didnt have to take part in Luffy's battle with Doffy PLUS ORGAN DAMAGE otherwise Luffy would have died. Well Sabo and Fuji could have stepped in but ya'll get me. Meanwhile Zoro's about to solo King lol I just dont see that much being needed for Zoro to put down King. (His Epithet as Joker more proof positive to where he'd rank but I digress)
So were talking YC1+ Strength, Conquerors haki, awakened DF, hax string fruit, haki mastery
Coupled with underworld brokerage, knowledge of the holylands national treasure, his bump for escaping impel down, having a marine infromant for 15+ years (No one mentions this no telling how many secrets he has from Vergo), weapons manufacturing and supply to various kingdoms, having the Mera Mera no Mi (and unintentionally having the number 2 of Revolutionaries eat it lol), wiping the memories/existence of thousands of citizens, marine officers, spys, people, enslaving those same people, dominating Dressrosa via blackmail, Flying from Marygeios, suplying a Yonko with smile fruits, then outright joining said Yonko in this hypothetical etc.
Doflamingo laundry list of crimes is wild. He literally is a wild card for the WG hence his moniker
I'd say 2 Billion but thats me