Kobe's work ethic was competitive for him, he was different than everyone else. It wasn't just his work ethic, but his demand for perfection and will to win. That all combined into this whole Mamba mentality we loved him for.
Yeah all athletes work hard (except Shaq lol), but Kobe was on another level. It's not marketing. If you followed him, you'd be able to tell. Just the fact that his peers, the best of the best, talked up (this is all in interviews and stories before his death) how crazy he was with his work ethic and how ruthless he was, it's something I've yet to see or hear from anyone.
One of my favorite stories was from a few years back, I can't remember the player who said this but I'm sure one of you guys can remind me, he was an opposing player not on lakers. He was talking about how he (himself, not Kobe) wanted to work harder than anyone else and he got to the gym for their game earlier than everyone to get practice in. Got there 4 hours early to be the first. Only, Kobe was already on the floor practicing.
He watched Kobe practice and then asked him why he's there so early, and Kobe told him something like "cause I saw you come in the building, and I wanted you to know that no matter how hard you work, I will always work harder".
Another awesome story was from I think one of the olympics, D Wade and someone else I forget, said that they had a team meeting that morning first thing in the morning. People were showing up yawning just having woken up but Kobe was there with his knees iced. He had already gotten in a 3 hour practice in and was recovering.
Shit like that man, there's countless more stories like this over the years of his own peers, people who are the best at what they do and they themselves are like WTF and in awe of Kobe's legendary work ethic and drive. He wasn't normal.