Natsu's endurance also likely matches if not exceeds Deku's as well. He can fight with broken bones just fine. He's been impaled by Gajeel all over his body and was barely fazed, he can survive several internal explosions that negate durability and only called the guy that caused them an inconvenience. He can withstand attacks that that would normally one shot him through sheer force of will alone
I'm voting Natsu via Zackra's reasons, but I want to say something against the bolded part.
One shot is such a worthless term nowadays, since what I considered a true one shot is not possible to survive without some special ability. But I know that a One-Shot in this wiki
doesn't always mean this (This is what I call a one shot). Since it can just mean knocking someone out in one hit, which can happen against someone weaker/comparable.
It's entirely possibly, for a weaker opponent to one hit KO a person if they don't have the stamina/endurance to take a punch to the chin. So whenever I see the term one shot, I have to remind myself to ask what does that mean. Since knocking out a person in one hit doesn't tell me anything, unless they do lots of damage as well.
Chimera in MHA one shotted Sato, but that was just a one hit KO. Sato was knocked out but woke up with only some bandages around his head and seemed fine. While Rappa didn't one shot Kirishima, but broke both of his arms in a single punch. The damage Kirishima took was greater than what Sato took, who had no broken bones.
A one shot like the scan above is instant death and impossible to survive with sheer will. Unless a person has Immortality, Regeneration, or can increase their durability. There are probably other abilities that'll let a person survive such a blow, but I'm not going to list all of them.
Either way, there goes my small rant about saying one shotting.
Also Izuku has no resistance against fire so Natsu's flames should just reduce him to ash, as they surpass Endeavor's flames which can do the same.