If Superman can become Pre-Crisis Superman Composite Superman Superman Prime Sun-dipped Superman and If Hulk can become Grey Hulk Savage Hulk Merged Hulk Mindless Hulk Maestro Hulk and etc etc then why not He has become Phoenix-Spider-Man and Uni-Spider-Man then why not. It's possible if Squirrel Girl Kazarr can beat Thanos and Puma can beat Beyonder then why not..
because the notion is ludicrous....no kind of Earthly science can generate the amount of power to take on a non-jobbing Darkseid AND Thanos...it just cant be done...especially by two guys who are constantly beaten by the X-Men...they may have genius intellects but your taking about Sky-father level characters here...and Banner pfff u coulda kept him outta this. + U coulda came up with a better conduit for the power like Juggernaut rather than a street-leveler like Spiderman...AND 5 days is not enough time to become proficient enough with his new powers to defeat them UNLESS he had SEVERE PIS and He went back in time to train for a million years then he last like 5 seconds.....
celestial tech is garbage....if it was so awe-inspiring War-Hulk would have killed Juggernaut instead of just knocking him back. Banner if he was so great would have better control over his gamma fused blood cells, or atleast cure himself and Sinister is good but he aint "beating Darkseid and Thanos" good.
Mister Sinister is a testament to what he is capable of he is damn near indestructible powerful and maybe immortal he did some of that If not all Of that to himself threw genetics Apocalpyse doesn't just have Celestial tech in wikipedia it says he has improved upon it that says how smart He is. As for Celestials tech they are responabile for the genetic creation of the Eternals,Deviants,maybe even the skrulls that pretty impressive. Plus it took Thor with a powerful hit to even crack there armor
How about Spider-Mans senses Hulks strength plus a nutrient bath courtesy of Banner and further augmentation from a genetic genius like both Mister Sinister & Apocalypse straight from Marvel themselfs Apocalypse possesses knowledge in certain areas of technology and biology, primarily genetics, which is far advanced from contemporary science.
Sinister from Marvel- Sinister is a genius geneticist, a brilliant biologist, and a skilled surgeon who is well practiced in the science of cloning.
Banner from Marvel- Dr. Bruce Banner is a genius in nuclear physics, possessing a mind so brilliant that it cannot be measured on any known intelligence test.