It seems to be the general consensus that Percy is the strongest demigod. I beg to differ. Jason is the strongest. Why? Simple
He can fly, while almost no one else can
Jason vs Piper
Is there really a contest?
Jason vs Annabeth
Again, no contest, Jason is far more powerful
Jason vs Reyna
Again, same thing as Annabeth, Reyna has no real powers, and is not as good as Jason combat wise
Jason vs Leo
Jason is faster, could doge Leo's fire balls, and Leo can't summon much fire before tiring out. Plus he could block the fire with his sword, and he could fly up so Leo can't reach him and lightning bolt him
Jason vs Hazel
Hazel's mist powers take time and energy to summon. Jason could kill her before she reacts with his sword, or with lightning
Jason vs Frank
Tough one, but Jason is a better duelist. Both can fly, since Frank can shape shift, but I do think, eventually, Jason would win. It's probably his hardest fight though.
Jason vs Nico
Here's where the flying becomes useful. Jason could fly up before Nico touches him, and Nico will be literally powerless. What can Nico do to Jason from the ground? Jason can them lightning bolt him, or just use the winds to throw him into the air a few dozen feet up, and then when he comes down and hits the earth, bye bye Nico
Jason vs Percy
Again, same thing. Just fly up, throw him up with the winds, lightning bolt him, or just let him fall back to the ground. Percy can' touch Jason is the latter flies up like 50 ft up. Even if Percy is fighting by the sea, he can't win, cause how cold he touch Jason if he flies up? Jason could again do the wind thing, and toss him around, dazing him. The he could lightning bolt him while Percy is dizzy. And if that doesn't kill him, he'll still be stunned, and can just swoop in and cut his head off.
Which is why I think Jason could beat everyone. This is the thing with these kinds of fights. If Person A can fly, and Person B can't, Person A immediately has a massive advantage. And for those of you who say "oh but Jason can only summon like one lightning bolt, and Percy could block it and then Jason would be tired", well Jason could just leisurely sit in a cloud and wait for his strength to return, and what could Percy do?