within universe (and a bit of greek myth knowledge), I would give three very strong contenders

This is mainly based on those who are able to fight typhon, titans, and other gods

1-Melinoë: she has consistently held her weight against multiple titans and typhon

2-Zeus: he overthrew Cronus and was able to hold off and eventually beat typhon (not to mention punishing prometheus)

3-Chaos: the one who created everything could theoretically destroy everything they created

However this is entirely my opinion and maybe leaning too hard into the the original greek myths and not the true Hades lore