Well, the Marine HQ/WG is one of the main forces standing in your way and the admirals their strongest forces. Yet,
1) Caramel calling Big Mom (fleet) admiral in terms of ranks and the strongest shield the Celestials could imagine, and Kaido > Big Mom
2) Oda putting Kaido > Akainu in the SBS
3) Shanks being their peer, fighting Kaido off
Given Luffy beat Kaido, I doubt he will fight Shanks, him not fighting Big Mom is clear too, despite Luffy initially saying he wants to beat all the Yonko and admirals.
So if the 4 Yonko were to face the 4 admirals, we know who would win.