Liking the story so far, let's see where this will go :)

"I take it you are a fellow sweat lover?"
Sweat is the liquid that forms on the body after exercise or on a hot day, sweet is a kind of taste, usually found in pastries.
Also I was expecting a ‘bat bat no mi’ devil fruit or some other batman themed fruit. cool story so far, I hope to see more.

Oh and how do you handle the fact that Big Mom can just teleport to your city through mirrors? You'd have to know well ahead of time to break all the mirrors on the island. Then what do you do after her crew is on the island with you? How do you stop logia like Kizaru or Enel?

why would i judge you on liking W.I.T.C.H., i quite like Winx Club. also he's Purple Haze!

This isn't a flame, just a few sincere questions.

Is your MC a moron, a coward, or both? I wonder if you're making him like that on purpose or are you trying to portray a likable character?

With so much foreknowledge about the One Piece and DC world, he spent 11 years fucking around doing absolutely nothing. I'm not sure if I want to continue reading if he countines like this.

so fugo and risotto nero's stands (purple haze and metallica) as a single devil fruit power? ok

so he has eaten some sort of plague/virus fruit? That is cool, if a little less versatile than i usually like unless you pull that one piece no-rules stuff with it and make zombie viruses or mind control viruses or since you mentioned MCU the extremis virus which i have always been a fan of.

Huh, this is a really interesting idea. I have seen variations but they all get their powers at the beginning and have evil as straight evil or good as a straight good. This one really brings the story onto a new path so nice job.

-SonOfThanatos11

That was rather curious, a very abrupt change in the flow, I don't know what to think yet, just hope whatever path the story goes Harley continue to show up

Gracias por el capítulo, fue bueno

Ugh man dont explain what happened or what will happen in the A.N at the end... whats the point of writing all those 9k words if u have to give a separate explanation regardless.

Also, its not a good idea to start another fanfic when this one is going slower than average. Focus on this one for a while more, or itll become even slower and people will lose interest.

:)

Love how this is going so far and currently needed to bang my head because the idea that some of the bigger characters getting genderbent got stuck in my head since it occasionally happens in evil self inserts and Oda actually does draw portraits for some like Mihawk, and the other Warlords, I think he did the Straw Hats crew not sure about others though, and some guy posted a meme with a female Katakuri on discord sigh anyways getting all that out of the way I really like how the story is going so far and the explanation on how the island is secret and doesn't like change really makes sense with how it's been set up, I look forwards to what comes next and if he does end up allied with Big Mom or Kaido I wonder how it will effect the story, actually to join Kaido you can take a short cut through Doflamingo or for Big Mom one of the crews subordinate to hers.

oh geez

Okay, this chapter is just...
Man, what the fuck is this even, I can't put to words!
1) The way MC SUDDENLY started feeling like being bad, that is just... Out of the left field and out of character. He helped keeping Joker sane, he sought to make would be criminals law abiding citizens and now he is dissatisfied by them not being evil? THE F!
2) Jumping from the grandpa to the Devil? THE FU!
3) The way Son went on and on about Supernatural, the TV Series, and then you went and talk about the show? THE FUC!
4) The way the meal was being had in Japan when Supernatural is a predominantly American show?
5) The way Evil itself was being so... Mr. Exposition? And SUCH a convoluted exposition at that?
6) The way MC got chosen because he liked the villains because they are the ones that deserve a win, like THAT is something special?
7) Offer of immortality, the offer of sudden dimensional travel, the offer of...

Okay. I think I talked enough about that utter bullshit.

Look. I am not a flamer. I know I never wrote this negative of a comment in ever.
I honestly think this chapter is just... Insanity. It breaks the flow so much that I want to yell "What the Fuck Are you Thinking?!" but it is your story.
The problem I am having accepting that reasoning, that its 'your story', is because I liked this story. I liked to see what became of it. I liked how original the setting was. I liked the idea of Batman on a ship, being a pirate. I liked the idea of some insane technology that is a combination of One Piece tech and Batman tech leading to insane events.

But instead I get cosmic horror totally out of the left field. You do not pull shit like that without some foreshadowing. How the HELL could we have thought MC getting answers about his grandfather leading to a face to face meeting with something that is blatantly trying to act like Death from Supernatural, saying that Supernatural's characters exists in the real world, and...
The rest of THAT...

We can't. We didn't. We don't.

Instead, here is the constructive part of my review, you should have done:
1) Focus on grandpa's research, don't reveal him for a few chapters, make us think he is a reincarnator too, then make us think he is somehow more than that.
2) Do not put in a meeting with the Evil. It is a Cosmic level thing, and you do NOT meet those things. Unless you want to enter a debate. Those things broke the balance of story. Their existence will hang over our heads for a long time then.
Instead make them use proxies, God has Metatron to relay His words, make Evil do that too. Or maybe take the route of Buffy and make Evil be a ghost of the departed with evil in them(and all humans have a bit of evil in them), so they shift into someone you lost to talk to you, to corrupt you.

3) Do NOT be EDGY. That EDGE is picto level sharp! Becoming Evil's Champion? Becoming the Immortal Champion of a Great Entity spoken in the same vein as God? Don't.
If you want to argue about this point then read the full title of your character.
Vince Arkham, Reincarnator, Heir To The Arkham Family, The Immortal Champion Of Evil.

4) Use the content of other settings in moderations, especially if they break from the flow of the story. You went from mystery to religion, you do not do that unless you've added religious moments sprinkled all around.

5) If you are making use of another setting's content then make sure the flows do not clash with itself. Meaning do not use a rich Japanese restaurant when you are trying to imitate meeting with Death in Supernatural. Death is a guy who likes fastfood, he is cheap, not classy, if he was then it would make him seem unaproachable, if you are trying for the opposite then make sure the floor matches the events.

6) Flow is God, do not break it. This story was one about relationships between Vince and the villains, since when did it turn from that and into one where he kills villains mercilessly and in as painful way as possible?
That shit does not fit his character! Nor does that fit into the character he is imitating, Batman Does Not Kill.
Nor does that fit into his back story either, he is a guy from the real world, and trust me people get quazy when they see death in real life. Just search Goatse, or other graphic images, they make you feel disturbed automatically, if he is still human then he wouldn't torture people...

Man, I am tired. I need to sleep already. And I am mentally tired of writing this comment. This whole time, through all the chapters I read, I felt like this story was going to hit a deadend. At every turn I felt like that, because it was clear you were trying to create something totally unique and original, and that was admirable but also incredibly hard to do. But you strived to keep on going, maybe you saw the warm reception and it egged you on but you did write it onto chapter 3.
I respect you for that.
But I do not respect you for the part past that glitching and meeting Evil.

I have a hunch that says you got tired of writing, it became too hard, so you rushed. You just wrote what came to your mind, and it seemed like good enough, a different direction that gave you inspiration.
Also at the same time you wanted to move on, you wanted to write some action, so you put a timeskip. Or maybe that was to attempt at a cliffhanger...

I am repeating myself. But please come back to this chapter and fix it. Or maybe go to the earlier chapters and edit them to make this tone shift more natural.