If we take the presentation that Cull is supposed to be Hulk level seriously then Scott CAN kill Hulk in 1 good hit or in a small number of bad hits....
Basically all the Wakandans need to do is form up the same firing line, unload, wait for the lucky ones and have a second line to deal with those in...
I also agree with Big in that I feel like Brian could pretty easily lift up a docile Ghidorah but the dude is a bit to spiky and sparky to man handle...