I'm more surprise They just keep forcing Nardo to do 3 or less clone for that clone jutsu rather than hey use as much chakra as you can to create as much clone as you can do. Because we all know clone jutsu can actually create as many as the Current wielder can do. Remember Sakura making 5 or 6 clone during the chuunin exam.It is funny to me that Iruka presumably had 3 graduation exams or whatever to fix Naruto's chakra control and it doesn't happen. He clearly has a shitload of chakra even in chapter 1. Performing a clone jutsu caused a small shockwave from his chakra before it failed so why the hell didn't they try beating control into him more. He doesn't need any real help with Taijutsu based on him beating one of his teachers face in. Yeah there's the leaf thing but still. The academy kinda sucks when you think about it. I used to think Ebisu was kinda pointless but the fact that he had to point the lack of control out so late in the game while Kakashi played favorites is pretty crazy
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Kakashi played favorites is pretty crazy
"What if you ignite the air in someone's lungs?" - That is NOT how Fire bending works. They either have to use their OWN breath to create fire or use fire that already exists.
"What if you make the water in their body explode?" - Damn it Shad, that is NOT how water or blood bending work. How the hell are you making it explode? I assume you meant to have it EXPAND, but we haven't seen anyone do that so.
"You have to be a BLOOD bender to do that?" - Blood benders ARE water benders mate, just high level ones. How do you think they're bending the blood in the first place? It's a little disingenuous to try and separate them from this discussion. Metal, lava and lightning bending should also be included.
Anyway the actual answer based on what we've seen in the show is air or water being the most outright deadly at top levels. In terms of just shooting elements at people like they were doing, it would be lightning bending.