The world of One Piece is filled with incredible abilities and characters, and Dewa Nika is one of the most fascinating powers that have been introduced in the series. This ability, once held by Joy Boy, makes Luffy unbeatable and has been seen during his fight with Kaido and CP0.
The power of Dewa Nika is so great that it has been compared to the legendary Joy Boy, who had this power before Luffy and is assumed to have reached the same level of awakening as Mugiwara. However, it has been revealed that this power was halted before and caused Joy Boy’s defeat.
If Joy Boy was indeed the previous user of Dewa Nika, it explains how the 20 Kingdoms alliance that brought down the Ancient Kingdom managed to stop its power. It also raises the possibility of Luffy facing the same fate when he confronts the World Government on Egghead Island.
The 20 Kingdoms, now the World Government, is the only organization with knowledge of the weaknesses of Dewa Nika that Luffy currently possesses. They have used this knowledge before to defeat Joy Boy, and it is possible that they may use it to defeat Luffy as well. However, Eiichiro Oda will not let Luffy die, especially since he is the main character of the series.
Although the power of Dewa Nika can be stopped, Luffy can still use it to its fullest potential to defeat his enemies, particularly the World Government. The method used to defeat Joy Boy may not be the same as the one used for Luffy, and Oda has yet to reveal all the events of the Void Century.
Dewa Nika also raises the theory that Luffy and Joy Boy may be the same person, but this has not been confirmed by Oda in One Piece manga chapter 1084. Regardless, the unmatched power of Dewa Nika and its connection to Joy Boy adds another layer of intrigue to the already complex and fascinating world of One Piece.