Hi, I hadn't planned on doing this, but after seeing people saying the protagonist wasn't strong, I decided to do it. Now, if we look at it from the perspective of the universe, like, I don't know, DC, the protagonist wouldn't be able to stand up to characters like Dr. Manhattan. But considering his current situation and the worlds he'll visit, I feel his power level is appropriate. If he were the most powerful, there wouldn't be any conflict in the universe; it would weaken the story, and it would force me into a ridiculous comedy, even more so than it already is.
Now, all of this is debatable, and if you think I'm wrong, you can tell me, but with some basis, not just your own impression. And, as I always say, if I find you're right, I'll say, "I messed up; you're right. now I'll see how I fix it."
Without further introduction, I will present the protagonist's powers, abilities, and weapons:
Physical Abilities: Superhuman strength, primarily focused on speed, with a fighting style that capitalizes on his opponents' mistakes and weaknesses. (Granted by the Constitution of the One Piece world.)
Haki: Mastery of all three types of Haki, using them at their maximum potential, easily on par with a Pirate King (Roger, Garp, and Whitebeard).
Death Fruit: Increased stats, enhanced stamina, and regeneration; grants him the ability to see lines on the bodies of living beings; when he severs them all, the target dies instantly and also grants him the ability to fly. He can also create spectacular bladed weapons. His awakening allows him to inflict death lines on any non-living being, in addition to other abilities not yet seen.
Murasama (Calamity Mod): A katana with sentience, capable of harming and killing Lovecraftian beings.
Darkness Fruit: I won't say much here now, as I have a theory about what this fruit actually does, beyond absorption, which I'll reveal when the protagonist is summoned as a Caster. But I'll just say that the ability to create real black holes is already something beyond the ordinary.
Alchemy Fruit: The ability to alter the chemical structure of objects, capable of converting elements into others and altering the structures of objects, whether organic or inorganic. In its awakening, it would be capable of altering even the air and the atmosphere (I don't know if I'll do this, but it's just an idea of what its awakening would be like).
Vampirism: Thanks to the soul-binding with a vampire, the protagonist can, if they wish, completely transform into a vampire. This further increases their stats and grants them virtually immortal regeneration, but with the weaknesses of a vampire.
Magic: A moderately acceptable level of magical proficiency; not very advanced, but capable of things like teleportation, increased strength and defense, shapeshifting, and object creation, among other abilities.
The Pure Bone Sickle: A weapon capable of removing the soul of a living being with a single cut. It can hypnotize, create portals to other dimensions, change size, temporarily store souls, and grant its user flight, among other powers.
Greek Sacred Bone: Can summon and manipulate the sacred bone given to Hestia for safekeeping, a flame that never goes out. It can be imbued into weapons or objects.
Kamigami no Gigan: With these eyes, he possesses the following abilities: Absolute Truth Vision (he can see through illusions, disguises, or deceptions); Conceptual Perception (he can see hidden objects such as oaths or additions); Intent Reading (like Haki); Time Vision (he can see past, present, or future, including alternate worlds); Dimensional Perception (he can see portals, rifts, or expanded spaces); Weakness Analysis; Hierarchy Recognition (he can distinguish between races, including divine or similar beings); Automatic World Translation (he can decipher any seal or language); Autonomous Activation (the user can act independently); Protection of the user (Containment); Resistance to Interference; and Observation without Interaction (he cannot alter reality).
(Here I copied and pasted the Servant section, but I added details to each ability.)
Well, that's all for now, since I don't remember the protagonist's Servant ability, and if he did have one, he would be stronger than he is now.
If anything is missing, I'll add it later. I hope this makes my point clear. Dante is strong, but I don't want to put him at the level of being able to destroy entire universes unless the threat he faces is of that magnitude; otherwise, he'd remain as he is.