Luffy would probably be the most interested. He loves a good fight and would be super excited to see all the action in the death battles.
Another character who could be really interested is Chopper. He's always eager to learn new things. Watching these death battles, he could be studying the physiology of the fighters, how they heal from injuries (or don't), and it could help him become a better doctor for the crew.
I think Sanji would also be very interested. He might be looking at how the fighters move and use their bodies, and also checking out any female fighters. He has an eye for combat and beauty, so he'd be into it. He might also get some inspiration for his own fighting style, especially when it comes to using his legs in combat.
One of the most popular death battle scenarios in One Piece fanfiction is the clash between the Straw Hats and the Blackbeard Pirates. It's exciting because both groups have strong and diverse members. Another popular one is a duel between Ace and Akainu re - imagined in a different way than in the original story. Also, battles between the yonko like Kaido and Big Mom are often written in fanfiction as death battles.
Well, it could involve the characters from One Piece watching intense death battles between various fighters. Maybe they're commenting on the fighting styles, like Luffy being amazed at some super - fast combatant's moves.
I think Whitebeard from One Piece would be a top contender. His quake - quake fruit gives him the ability to cause massive destruction. But Percy has his own set of skills. He can heal himself to an extent with water and has a lot of combat training. On the Percy Jackson side, Annabeth is also very smart and could come up with strategies. In a battle, she might be able to find weaknesses in the One Piece characters. But in One Piece, characters like Doflamingo with his string - string fruit can be very tricky opponents too.
In a fanfiction death battle between Luffy and Zoro, it's really tough to say. Luffy has his rubber powers which give him great flexibility and his Gear forms that boost his strength tremendously. However, Zoro is an incredibly skilled swordsman with his three - sword style. He has great strength and speed too. But I would say Luffy might have an edge. His ability to stretch and his unpredictability could give Zoro a hard time in a fight to the death.
Ben himself is obviously very popular. After all, it's his Omnitrix that's the centerpiece. Then there's Four Arms, who is often included because of his brute strength. Vilgax is also a common one as he is a major villain in the Ben 10 series and makes for a great antagonist in the Death Battle scenarios.
I think it could be a toss - up between Goku and Whitebeard. Goku has his incredible ki attacks and speed, but Whitebeard had the power to cause earthquakes and was considered one of the strongest pirates in the One Piece world. If Whitebeard were to face Goku, his experience and the power of his Devil Fruit could potentially give him an advantage, especially if he caught Goku off - guard.
It's really hard to say. Luffy has his Gear Fourth form and the ability to stretch his body in incredible ways. But Naruto in his Sage of Six Paths mode is extremely powerful too. He has access to a vast amount of chakra and can use some of the most powerful jutsu. However, if we consider Kaido from One Piece, with his near - indestructible body, he would also be a top contender. So it could be any of them depending on how the crossover is written.
Definitely Batman and Luffy. Luffy's carefree and positive attitude would contrast with Batman's brooding nature. But they both have a strong sense of justice. Luffy punches bad guys, and Batman uses his gadgets and martial arts. They could learn a lot from each other. Another interesting pair could be Robin and Alfred. Alfred's wisdom and knowledge could help Robin understand more about the history and culture in Batman's world, while Robin could share her knowledge of the Poneglyphs with Alfred.
It's hard to say for sure. Luffy has the power of the Gum - Gum Fruit and his Haki, which gives him great strength and the ability to sense and overpower opponents. However, Naruto has the Nine - Tails' chakra and Sage Mode. In a crossover, if they were to fight, it might depend on the situation. But if we consider all - round power, Naruto's ability to create multiple clones and use a variety of jutsu might give him an edge over Luffy in some scenarios.
I think Nami could be fascinating. In a DxD setting, she could use her wits and charm to manipulate some of the Devils and Angels, just like she does with pirates in One Piece. Also, her knowledge of navigation and treasure hunting could give her a unique role in the DxD universe, perhaps leading her to discover some hidden treasures related to the different factions.