What you consistently find is that it's never said "one emperor" but instead has always said all four emperors.
Stop talking bullshit.
1. Garp Says that Navy will not be easy against two legends.
2. Ivankov says that the government is joking when opposing Dragon and WB.
3. Vice Admiral says that during the battle with WB, the Navy will not be able to devote time to the battle of Kaido and Shanks.
4. Orochi says they won’t defeat Kaido
5. Koby's words about all the forces of Navy against shichibukai
6. Garp's words about the Kaido Alliance and BM. It is beyond imagination
7. The war against the sick and the old WB where all the forces of Navy and shichibukai came out.
8. Sengoku's words that they can lose the war
9. Koby's surprise at the yonko alliance. Since this is almost an unrealistic thing.
10. Shanks stops the war in one word.
11. The whole world wonders who will win WB or Navy.
12. Grandma Boa admits that WB can win the war against the government
13. The government is doing everything in its power to prevent Shanks and Edward from meeting.
14. Shutenmaru says own territory is an advantage. And after all there was a war against sick Whitebeard.
15. Teach says that Whitebeard could not save Ace due to old age.
16. Shiki says that he and Roger alone can conquer the whole world.
17. BM and Kaido say they can conquer the world
18. You need preparation with an admiral to defeat Ray
19. Against Ray you need half of Navy
20. One yonko flag gives protection to an entire island
21. Judge chooses yonko and not government to conquer the North Sea.
22. Almost all Shichibukai are friends with yonko: Doflamingo, Mihawk, Jimbei. That already indicates the impossibility of such a balance.
23. Watch to defeat Whitebeard resorted to dirty tricks. Let me remind you that this is an old and sick Whitebeard. Who himself admitted in his thoughts that he cannot always be the strongest.
24. BM says that with Elbaf she will become a PK. And to become a PK in manga you need to defeat the admirals and yonko. That is, with Elbaf BM is stronger than all.
25. Doflamingo thinks who rules the sea ONE OF YONKO, Navy, RA, worstgen, or shichibukai.
26. Koby hopes that yonko will fight each other and just in shock from the alliance.
27. Navy, according to Garp, may not allow the meeting of two yonko. And DO NOT WIN two yonko.
28. According to Garp and Doflamingo, Whitebeard RULES OF THE SEA (at this time, Doflamingo does not know who rules the seas. Even if NAVY, then this is a small advantage).
29. Navy's power is not enough to defeat Rox pirates. They need Roger's crew.
30. Doflamingo wanted to kill Fujitora. Doflamingo didn't want to kill Kaido.
31. The alliance of the Marines with the Shichibukai was formed over 11 years ago.
Then there was no Shanks and half of the emperors' crew were very young
32.
According to Akainu, Kaido and Linlin's alliance may tip the balance against them.
33. "I WOULDN'T HAVE EXPECTED THIS TO HAPPEN" - Sengoku about the alliance between Kaido and BM
CAN YOU SHOW ME JUST ONE SCAN WHERE SAID THAT THE NAVY AND THE WARLORDS ARE ABLE TO DEFEAT AT LEAST TWO YONKOS AT THE SAME TIME?
NO, YOU CAN'T.