Endeavor could vaporize enemies literally made of plasma with his fire.
Vaporizing means turning something into vapor/gas, knowing what plasma is, this sounds like you're saying he cooled it down with his flames.
Which is the exact opposite of what you're trying to say.
To give my opinion on the fight. Endeavor is only 1.179x weaker than Omni-Man, barely a noticeable difference. So their actual attacks would inflict similar damage to each other, with Omni-Man's being very slightly higher. His superior experience is mostly offscreen guess work, as we don't really know what he can do.
His actual showings at this point is nothing Endeavor hasn't dealt with before. Endeavor also has superior Lifting Strength, meaning he'll find it easier to keep Omni-Man off of him. As a single fire blast will knock him away as he can't withstand the force, this prevents Omni-Man from overwhelming him up close.
Endeavor can also restrain him if he manages to grab him as well. As long as he does it correctly, he can lay down damage on Omni-Man while he can't move.
IDK about Omni-Man's heat resistance but Endeavor's flames scale far about Bakugo's 5000°C explosions and above the temp needed to turn people into plasma. Don't know exactly what that is since I've gotten conflicted reports on this. But heat resistance doesn't stop the fact Omni-Man will still take damage.
Even if we say he doesn't get burned, the actual physical impact will affect him, as it's 877.51 GT. Endeavor is a ranged fighter while Omni-Man is a close range fighter, meaning Endeavor has the advantage when at a distance. And his sheer AOE can keep Omni-Man away from him.
In terms of Flight Omni-Man is better, but I don't think he's doing anything Endeavor cannot handle. He's more than capable of moving freely throughout the air with his propulsion. Also, he doesn't fly just through his feet. He can make that propulsion anywhere on his body for rapid movement.
Think the fight is more fair than people are making it seem.
