I don’t get why this is such a hard concept to accept. Luffy was a tough ass kid. Koby was definition of a wimp who lost his way. Sure he trained with Garp, his growth is still amazing, that is crazy growth. Anyone trying to tell u differently is just wrong. Another thing is the assumption that Garp trained him everyday. That’s not even true, as soon as koby and helmepo joined the marines Garp didn’t train them until what we perceive days later.