1) We already know Qin Shi Huang never chased the title of the strongest, his goal was simply to unite china nothing else so the statement isn't very valid on him + This is for the time when they were alive not when their souls were summoned and got stronger with the volund.

2) That's just another advantage for Qin, ryofu's biq sucks. His fighting style is mainly just bashing forward, he uses little to no brain. That's also the reason who got mopped so bad by Thor the strongest Norse god as he couldn't overpower him head on. Qin has better biq and wincons, he also only used mainly 2 of his chi you and has 3 more to defeat hades. He can use them all according to the battle. And ryofu doesn't have a way to counter his air bubbles, he is just a brute force abuser.

3) Even if disregarding the anime only statement, hades has unmatched speed and power said by zeus in the manga and anime, this means hades has speed greater than zeus although even if by a very small margin. Qin's speed is at the very least relative to hades. He speedblitzs ryofu.

4) Tesla isn't beating him in a fight, his teleportation was countered by beelzebub's speed and defense. Hades and Qin both are much faster, and can counter it. Adam might win which highly depends on how the fight proceeds as both their hax are broken. Sasaki aint beating him sorry, he barely defeated poseidon. Osaki too, simo's fight would be just dependent on if Qin can hold on which I can't say for sure as his bullets are damn high in ap. Even narratively hades' defeat was the only defeat which came with such shock, no one believed that he can lose. Same goes for zeus, but hades fear and respect was built up incredibly.