Endeavor's flames, are very close to being Hundreds of meters in range, I got them being around 90+ meters. And Endeavor is far more mobile than any of the heroes he faced, not including Bang, thanks to his flight and propulsion. And he's been shown to avoid attack from characters who are faster than himself.
A big difference being that Endeavor is a ranged fighter, while Melzalgald range is inferior. Meaning he'll have a harder time hitting Endeavor than the other way around. And if their attacks meet, he's just going to burn his body away with his flames.
Don't see anything to suggest Bang was knocked out, when he comes back like a few seconds later rolling his shoulders, and he seems completely uninjured but whatever.
Also, I'm pretty sure a Prominence Burn would kill Melzalgald unless he dodges it. It'd instantly vaporize every part of his body, and destroy those marbles. Endeavor has been shown to
easily melt glass, assuming those things share the same melting point as actual marbles which are usually made of glass. Note: Yes the anime does exaggerates things, he didn't melt the entire thing in the manga,
but is still shown to have melted the inside of it.
But even ignoring that, those things aren't very durable regardless considering how easily Metal Bat breaks them, who is Low 7-B at his strongest.
The Shigaraki comparison is rather not accurate, when Melzalgald is slower than Shigaraki with speed equalized, and is a far bigger target for Endeavor's flames. Shigaraki was more mobile too, being able to punch off the air to avoid Endeavor's attacks. While Melzalgald hasn't been shown to be very mobile or quick to dodge.
Also I believe that Endeavor could take a direct hit from him, not counting any bladed attacks for obvious reasons.
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