It's always interesting to see Spider-Man fight a "baddie" that fans arent accustomed to. Mostly because they don't know how the fight will turn out, or the extent of said enemy's power and strength. Spider-Man himself, is considered to be one of the most over-powered super-heroes in the Marvel universe, having super strength, agility, endurance. Plus his spider-senses are a major advantage over any enemy. So whichever bad-guy he fights needs to be of equal danger, or equal cunning. There's just one problem: Spider-Man has a lot of enemies.
The list of Spider-Man villains is as long as Batman's villains, arguably longer. Because of this, it's very easy to forget who is a classic villain, and who is just a recurring villain. Just because a villain is famous for being an iconic Spider-Man enemy, does not mean they were a a classic enemy.
10 The Chameleon
Excluding the burglar who shot Uncle Ben, the Chameleon is the very first Spider-Man villain to join his rogues gallery. First appearing in The Amazing Spider-Man #1, Dmitri Smerdyakov, or the Chameleon as he professionally known, entered the comic-book stage disguised as Spider-Man after figuring out the web-slinger was desperate for cash because of his failed attempt to join the Fantastic Four. He attempts to steal some missile plans from a military base, and is able to place the blame on Spider-Man using his disguise. Spider-Man stops him, but the Chameleon is able to disguise himself as one of the military guards, escaping and successfully placing the blame on Spider-Man. For a first entrance, this was a really good start.
9 The Vulture (Adrian Toomes)
Made substantially more famous by the film Spider-Man: Homecoming, the first iteration of the vulture has a fairly tragic backstory. As explained in The Amazing Spider-Man #2, Toomees was a genius inventor who was betrayed by his business partner who was stealing funds behind Toomes back. This forced him to a life of crime in order to get revenge. His costume is actually an electromagnetic harnes that extends his lifespan and allows him to carry a pair of artificial wings on his back. He made his first appearance by purposely failing to rob a jewelry-exchange while flying. He then returns the next day and robs them without flying while they were expecting him to fly in. He is captured by Spider-Man later that issue.
8 The Tinkerer
Also appearing in The Amazing Spider-Man #2, the tinkerer is a pretty fun character. He's an old man but also a highly intelligent genius, who is literally able to invent anything from spare junk, and then sells it to the criminal underworld from his "Radio Repair Shop." In his introductory storyline, Phineas Mason - aka the Terrible Tinkerer - hires some thugs to place bugs in the radios of politicians in order to blackmail them.
When Spider-Man figures this out, he enters Mason's hideout, only to find aliens who escape in a flying saucer. This was later revealed to be a genius ruse by the Tinkerer, who was wearing a costume and had a spaceship shaped hovercraft. That's pretty meta and genius for his first appearance.
7 Doctor Octopus
One of Spider-Man's original arch-Enemies, the man known as Doctor Octopus (Dr. Otto Gunther Octavius) made his first appearance in The Amazing Spider-Man #3, and was the first Spider-Man villain to have an entire issue to himself. Like most Spider-Man villains, his backstory is pretty tragic, filled with lost love, matricide, unappreciative colleagues and freak-accidents; Doctor Octopus entered the criminal stage at a point when Spider-Man was no longer challenged by the criminals he fought. When they both crossed paths in the hospital where Octavius was recovering from his accident, Spider-Man failed to best the new foe, and only defeated him after being motivated by non-other than the Human Torch. Since then, he returned in later issues and became Spider-Mans nemesis before even the Green Goblin was introduced.
6 The Sandman
Born William Baker, although he would later adopt the name Flint Marko, the Sandman is one of those villains who just existed n his introduction. In The Amazing Spider-Man #4, the Sandman was introduced as The Sandman; fans don't learn of his origin story until later in the issue and only through police chatter (albeit, it was drawn out so readers could see it). He was an escaped convict who turned into a literally sand-man after coming into contact with irradiated sand, which changes his molecules into sand. In the issue, he hides on a beach, robs a bank, and defeats Spider-Man, and even tries to get a high-school diploma from Peter's principal.
5 The Lizard
Curt Conners, a classic Spider-Man ally, is also The Lizard! First appearing The Amazing Spider-Man #6, Connors was a scientist living in the Florida swamps working on a serum that would help him regrow his lost arm.
The serum worked, but created a second, reptilian-humanoid personality known as the Lizard. This was the first Spider-Man villain defeated outside of New York City, and a fan-favorite recurring character. He often transformed back into the Lizard due to stress, or exposure to chemicals while working to help Spider-Man.
4 The Living Brain
A lesser known Spider-Man rogue, The Living Brain is a hyper-intelligent robot who can deduce the answer to anything using mathematics. He first appeared in The Amazing Spider-Man # as a simple machine that could answer anything, with the express intent of helping solve the worlds problems. But two of the henchmen hired to move it while it's on display at Peter's high-school, decide to use it to win at gambling. When the machines creator, Dr. Petty, catch the men trying the steal the Living Brain, they accidently cause the machines controls to malfunction, which makes it go on a rampage. New fans of Spider-Man might recognize the character as being an assistant of Otto Octavius, the Superior Spider-Man.
3 Electro
Maxwell Dillon, aka Electro, was an electrical engineer who got struck by lighting while repairing a power-line. Electro is the first Spider-Man villain thought to be a Mutant, as he was approached by Magneto in the near future. Considered a power-house marvel super-villain, he appeared in The Amazing Spider-Man #9, where he was free from being defeated by the spider because of personal issues at home. In the issue, Peter actually forged a picture of Electro turning out to be Spider-Man, in order to get a thousand dollars from J. Jonah Jameson for an operation Aunt May required. He became the first marvel villain to be written to be battling Daredevil.
2 The Enforcers
Known by hardcore Spider-Man fans, Montana, Ox, and Fancy Dan are the Enforcers. A group of thugs/hired-muscle that help commit underworld schemes and assisted the notorious Big Man of crime in taking over the criminal underworld. They appeared in The Amazing Spider-Man #10, and continued to show up in later issues before crossing over into other titles. They made a vague appearance in Spider-Man: Homecoming, since the group ran by Michael Keaton's Adrian Toomes were called The Enforcers. Other than that, they aren't very popular, but recognized as original Spider-Man Rogues Gallery members.
1 Mysterio
Mysterio made his official debut in The Amazing Spider-Man #13, framing Spider-Man for a museum robbery he committed while dressed as him. He then tries to defeat Spider-Man while playing the hero-persona, tricking Spider-Man using smoke and other film-effects. But he foolishly admits he robbed the museum and framed the web-slinger on camera. It was even revealed that the supposedly aliens in the Tinkerer's hideout in The Amazing Spider-Man #2, were actually Mysterio hired by the Tinkerer.