1 Whitebeard, The World's Strongest Man Captain of the Whitebeard Pirates, Whitebeard was one of the strongest pirates of Roger's time.
Roger's first and perhaps his most formidable rival and greatest enemy was Rocks D. Xebec, the captain of the legendary Rocks Pirates who sought to become the king of the world.
Garp, said to have cornered Roger multiple times before his surrender, as well as Roger's second foremost pirate rival Whitebeard, who held the power of the strongest Paramecia Devil Fruit and was called the "Strongest Man in the World", even before Roger's death. Another person known to rival Roger was Rocks D. Xebec.
Whitebeard was a legendary pirate, but not even he managed to shake things up like his rival, Roger. However, as fate would have it, another person would be born five years after Roger's execution, and he would become one of the most infamous pirates in the world, and that person was none other than Monkey D. Luffy.
Kozuki Oden
He was the second division commander of the Whitebeard Pirates.
Portgas D. Ace, born as Gol D. Ace and nicknamed "Fire Fist" Ace, was the sworn older brother of Luffy and Sabo, and the biological son of the late Pirate King, Gol D. Roger, and Portgas D. Rouge. Ace was adopted by Monkey D. Garp, as had been requested by Roger before his execution.
Dragon is the son of the famous Vice-Admiral Monkey D. Garp. No direct interaction has been seen between father and son. However, Garp was casual towards telling Luffy about Dragon's criminal status, going so far as to pick his nose while saying this.
Roger and his men, as seen during the Oden flashback, would simply be too strong for Luffy to defeat in a fight.
Luffy is close to Shanks in terms of power and it is only after their fight that he will officially be able to call himself stronger than Shanks.
He is also part of the 11 troublemaking pirate rookies called the "Worst Generation", alongside with his archenemy, Marshall D. Teach (Blackbeard).
Roger was called the Pirate King. But sadly he did not have a Devil Fruit power. From what we have seen from flashbacks, Roger solely relied on his Haki in battle. He was strong enough to fight foes like Whitebeard and Kozuki Oden.
Gol D. Roger was executed by the world government. Execution is a pretty common punishment for piracy in the One Piece world. (That, and a prison sentence to Impel Down for life without parole.)
2 Can Defeat: Gol D.
His real powers are yet to be seen but as the series has progressed, he has been portrayed as the strongest character in One Piece, alongside Whitebeard. If Shanks were to fight Roger, he would get defeated by him easily.
Roger could possibly beat any character in the series. Although he isn't alive right now, he did clash with Kaido at God Valley where the Rocks crew was annihilated. Arduous as it may be, it is expected of the Pirate King to be able to take on Kaido without much trouble.
Roronoa Zoro - The number two of Strawhat Pirates, and Luffy's right-hand man.
Luffy got his scar on his chest from Roronoa Zoro this happened while Zoro's being controlled on Episode 223 from 10:55 - 11:10.
Shanks' scar caused by Blackbeard because he's mistaking the gomu no mi with yami no mi which Blackbeard been searching for decades.
Gear 10th Luffy is Luffy's ultimate form from the upcoming speculative fan-made sequel to One Piece, Son of the Pirate King. Luffy has continuously trained his haki and Devil Fruit powers during his time as Pirate King until he achieved this gear.
The concept of power up Gears has been a core part of the One Piece franchise and allowed Luffy to take on the most difficult of foes. Fans speculate Gear 6 is inevitable – and with the series winding up to its conclusion, it could play a pivotal part in the final conflict.
Additionally, Garp is generally amused by Luffy's exploits as a pirate, and only seriously laments both of his grandsons' choices to become pirates after Ace is captured. He also ultimately allowed Luffy to hit him due to valuing his family more than his duty as a Marine during the war at Marineford.
Who is Zoro's father? Roronoa Arashi is confirmed to be the father of our beloved swordsman, Roronoa Zoro.
Garp is known to possess immense Haki and as fans know, he does not have a Devil Fruit ability. As such, fans will most likely see the level of his Haki power in the upcoming chapters of the story where he clashes against Yonko Blackbeard.
Luffy is the protagonist of the anime/manga series One Piece and the love interest of the pirate Empress Boa Hancock.