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.
Garp has no devil fruit, but his insane haki makes up for it. He was able to flatten the head of Don Chinjao with just one punch. Garp could also destroy mountains with his fists. Garp is respected by both Marines and pirates.
With his fists alone, Garp can crush mountains. Garp confirmed that, while training to fight Chinjao, he destroyed several mountains with ease. Garp can also launch cannonballs with incredible speed at his opponents.
Also, one side of his face was seen starting to get frozen by Aokiji's Time Capsule power. While this manga panel certainly makes it look like Aokiji killed Garp, and he died on Hachinosu Island, we(and many fans) still believe Garp's role in the One Piece story hasn't concluded yet.
Monkey D. Luffy
This often leads Luffy to receiving the force of Garp's punches, and due to these experiences, he has become afraid of his grandfather. Garp also claims Luffy was poisoned by Shanks with ideas of becoming a pirate, as Garp wanted Luffy to be a great Marine like him.
Nonetheless, he cares deeply for his grandson and has shown to be proud of some of his achievements. Luffy loves, but also fears, his grandfather. However, the two get along quite well with each other, often laughing or scolding one another. It is unknown how Garp came into custody of Luffy.
He is a specialist of Observation Haki, Ryuo, and also Conqueror's Haki. Among all the Haki types, however, Luffy is especially skilled at using Conqueror's Haki, which is his best Haki type. In Wano Country, he reached Yonko level and is currently fighting Kaido in a one-on-one battle.
Monkey D. Luffy has mastered all three types of haki, including Kenbunshoku Haki (Observation Haki), Busoshoku Haki (Armament Haki), and Haoshoku Haki (Conqueror's Haki). He can even use several subforms of the hakis, which makes him one of the most powerful haki users in the One Piece world.
Saving Ace would have gone against Garp's loyalty to the Marines. After all, Ace was not just any pirate; he was the son of the Pirate King Gol D. Roger himself, and his execution was seen as a crucial step in the fight against piracy.
Garp Is Considered To Be One Of The Strongest Marines. Also renowned as 'Garp The Hero' and 'Garp The Fist', Monkey D. Garp is a Vice-Admiral of the Marines. Being their strongest known member in history, there's no denying that Garp is capable of taking on Kaido.
In his prime, Garp contended with monstrously powerful pirates. While fans haven't seen much of that, the series has dropped bits over time that confirm his strength as a mighty powerful pirate. Garp is known to be a direct rival of the Pirate King, Gol D. Roger.
Garp is a tall, broad-chested, muscular Gray-haired man who is bearded and has a scar on his left eye. Due to the fact that he had showen his face in the past, he wore a dog mask when he was first introduced, so nobody would realize he was Luffy's grandfather. When this fact was revealed he discarded the mask.
His Haki seems to be incredibly powerful. Even though Garp is very old, the Haki that he exuded during his assault on the Blackbeard Pirates was nothing short of staggering for the fans to witness. Along with Shanks, Luffy, and Kaido, this is the best display of Conqueror's Haki that fans have seen so far.
In fact, Nami has already demonstrated abilities similar to Haki. During the Alabasta Saga, she has shown the ability to tell even the slightest of changes in weather which, according to Vivi, is beyond human comprehension.
However, physical blows without Haki don't work on him due to his rubber body, and the only slashing-style ninjutsu Sakura is shown to know is a scalpel-like blade. With that being her only weapon to hurt Luffy with, it's likely she will lose this fight in embarrassing fashion.
Conqueror's Haki is one of the rarest powers to exist in the One Piece world. Unlike the other two Haki forms, this power isn't accessible by everyone but exists within only a chosen few. Its basic level allows the user to intimidate and overwhelm those who have weaker wills.
Shanks is recognized as the master of conqueror's haki and the killer of observation haki too. He is also one of the few pirates who can use all three types of haki. Shanks has mastered conqueror's haki and made several members of the Whitebeard pirate crew faint during his visit.
In the Post-War arc, one of the Five Elders stated that "D." means danger. After the timeskip, Law mentioned the Will of D. once more when Doflamingo asked him why he had so much faith in Luffy.
Following the events of Marineford War and Ace's death, he retired from his vice admiral duties and became a Marine Instructor, taking on new recruits in the new generation. Due to Cross Guild, Garp have a 3 crowns bounty worth 3.000,000,000 which stated to compare Cross Guild's bounty for Admirals.
Does he have a personal vendetta against Shanks and wants to kill him? No, that's not Garp. As much as he was against it, Garp understood that Luffy's way of life was his own decision. It wasn't Shanks who ultimately forced the pirate life style on him.