I'd actually go with Issei, due to his latest fight with a Heavenly Dragon class Evil Dragon who was literally destroying his body from all over during their fight. Not to mention he was able to keep fighting against Rizevim even though he was getting he ass kicked, and mind you, Rizevim is the son of the original Lucifer, and he tanked a giant light spear from Michael. Michael, the former ruler of heaven, and he took a giant light spear like it was nothing.



Also, no, Natsu would not be able to absorb a Dragon Shot due to how they are not fire or lightening based attacks. Basically, this fight comes down to who is the smartest, and I'd go with Issei, because the guy adapts much quicker then Natsu. Issei uses fire once, Natsu ears, Issei doesn't use fire the rest of the fight and instead uses his vast arsenal of abilities and attacks while figuring out a way to but Natsu down. He beat Cao Cao in a match of wits, and mind you, Cao Cao is a genius when it comes to tactics. So I'm putting my money on the Harem King, the Dragon Devil God, Issei Hyoudou.