The following abilities are considered godmodding. They are explained further below.
Naturally, this can never be done in an RP. It can be done in an original story, such as with a villain, but it's most advised for them to have an exploitable weakness. A main character with invincibility, though, should never be done. It would make for an incredibly boring story, what with no one being able to hurt the main character. A story isn't a story without struggle and hardship.
Light Speed Edit
This should NEVER be done. It's just impossible. The speed of sound is a good cap on speed.
Naturally, there are exceptions, such as Admiral Kizaru. But that's because he can turn into light. And that's not really possible for anyone else.
Inhuman strength Edit
This can be excusable, what with the prevalence of Super-Human Strength in One Piece.
Impenetrable Defenses Edit
This should NEVER be done. No defense can be perfect. Otherwise, it's the same as invincibility.
Living Forever Edit
It's just not possible in the One Piece world.
Naturally, Brook is a special case.
Reality Manipulation Edit
This should NEVER EVER be done. Trafalgar Law already borders on breaking this rule. Manipulation of reality makes a character the ultimate godmodder. It also creates a lot of holes in the fabric of the story and RP. Even reality manipulation in a localized area should never be done. This power is the first and worst of the "Unholy Trinity", a trio of three fictional powers that should never be used in a roleplay.
Human Puppetry/Mind Control Edit
Note that in an original story or fanfiction, this is perfectly alright. But this should never EVER be done in a roleplay. This is the second of the "Unholy Trinity". And, technically, Donquixote Doflamingo already has this ability anyway.
This is the third and least offensive of the "Unholy Trinity". This power is perfectly fine in an original story, but it's EXTREMELY inadvisable to use this power in a roleplay (though not outright banned). The reason is that this power is easy to abuse and get cheezy with. But mind-reading can be alright (if not a bit annoying to some other members of the RP) if used responsibly and maturely.