Kraven The Hunter happens to be the brother of Cameleon, but they are nothing alike. Kraven’s name is literal, he’s a big-game hunter who loves going after the biggest and most difficult threats. He considers himself to be the world’s greatest hunter and loves a challenge. This made him want to go after characters with animal-like names. That includes Black Panther, whom he hunted but was not as successful going after. Eventually, Spider-Man becomes his target, leading to him becoming one of the most notable Spider-Man villains ever. He’s unsuccessful many times but eventually does succeed in taking out Spider-Man… sort of.
This is part of the infamous Kraven’s Last Hunt storyline. Which is all about Kraven taking out Parker, then becoming the new Spider-Man to prove he can do the job better. Of course, Parker was not really ended by Kraven and eventually stops him. But the two have numerous battles, where Kraven never holds back. Spider-Man often does, which puts him at a big disadvantage. Kraven is an experienced tracker and tactician, so there is really nowhere Spider-Man can hide. He has to take on Kraven head-on. Due to the weapons and traps he uses, he is already difficult. Yet he will also use others to force Spider-Man out. Nothing is off-limits for this man.
Norman Osborn is a very wealthy man, which was built on his genius-level intellect, who is initially considered a relatively good man. But once he used a Goblin formula, his brain was altered. This possesses him to do a lot of odd, crazy things whenever the “goblin” inside takes over. This formula actually enhanced Osborn pretty significantly in several areas. Once it effectively went into his system, Norman had enhanced strength, speed, agility, stamina, durability, and reflexes. On top of that, he was also able to develop regeneration abilities.
Now going by the name Green Goblin, he develops technology to assist him in his new criminal ways. This includes several goblin-themed weapons like the infamous pumpkin bombs. This is on top of the Goblin Glider. He’s often portrayed as Spider-Man’s greatest enemy, not just one of the Spider-Man villains he sees on rare occasions. However, this is likely due to how personal he affects Spider-Man and Peter Parker. Likely the biggest story he’s connected to is the death of Gwen Stacy, yet he also attacks several others close to Parker. There is not a line Goblin won’t cross, and he only does what he does simply out of hatred for Spidey. Nothing more.
Dr. Otto Octavius was originally a gifted scientist who was considered a good person. He actually was working on a robotics project, which resembled the tentacles of an octopus. He was making them for use in numerous areas, especially for other scientists. They’re just worn on the back of the body and everything is operated by the user’s mind or movements. Yet the harness and tentacles become fused to his body during a lab accident. At one point, the story was that the tentacles somehow affected Otto’s brain. Since they were initially made to move with the thoughts of the user, they could easily mess up and do just the opposite. That seemed to be the case for Otto and his decision-making. Thus, he turns to a life of crime, becoming one of the top Spider-Man villains along the way.
Yet he eventually grows obsessed with taking down Spider-Man. This led to Octavius developing the Sinister Six team. He also learns Spider-Man’s identity as Peter Parker but has usually kept it to himself rather than tell others. Which seemed to pay off, as he was getting close to death during the 2012 Dying Wish storyline. He felt he could survive if he could switch bodies, but that is impossible..until it wasn’t. Otto somehow switched bodies with Peter, then lets him die in his body. That led to Otto becoming the “Superior Spider-Man,” where he wanted to prove he could be a better Spider-Man. While Peter is eventually resurrected, the movement into Parker’s body made him leave crime behind. But the fact that the original Spider-Man was killed and replaced by Otto is something no one else can claim.