Doctor Octopus is one of the best Marvel Cinematic Universe.
There are many versions of Doctor Octopus, but they all stem from the comic book original. Otto Octavius has been menacing Spider-Man since the very beginning. His comic book history is as long and complex as the Wall-Crawler's and in many cases, nearly indistinguishable.
The First Villain To Defeat Spider-Man
Doctor Octopus first appeared in The Amazing Spider-Man #3 in July 1963, the brainchild of Stan Lee and Steve Ditko. Doc Ock as he quickly became known to fans established himself as a major threat to the young Spider-Man right away, becoming the first supervillain to defeat Spidey in battle.
This led Peter Parker to consider giving up crime-fighting, but Spider-Man never quits. He teamed up with the Human Torch from the Fantastic Four and got the better of Doc Ock in the end.
Founded The Sinister Six
Doctor Octopus does not like to lose. His fragile ego led to his criminal exploits in the first place and later, his obsession with defeating Spider-Man. He founded the Sinister Six, a superteam of some of Spider-Man's greatest villains, including Electro, Vulture, Sandman, Mysterio, and Kraven the Hunter.
Many of those villains have made appearances in the MCU or are about to. With the news about Molina, it's an open question of who else could form an MCU Sinister Six.
The Master Planner
Doc Ock's desperation to defeat Spider-Man led to some interesting decisions. He once disguised himself as a villain called the Master Planner in an effort to hide his efforts.
This didn't work out, but it did lead to one of Spidey's most harrowing moments. In a battle over a formula Spider-Man needed to cure Aunt May, he was trapped beneath the rubble of a building. His determined effort to escape became one of the most iconic sequences in comics and provided one of the best covers ever by Steve Ditko.
Arachnophobic
These days, people might say Spider-Man lives in Doctor Octopus' head rent-free. That was certainly evident in their early encounters. Octavius' obsession with Spider-Man turned to fear after a major battle in which Spider-Man defeated him. After, Doc Ock became arachnophobic and afraid of all spiders.
This incident came as a result of Doctor Octopus' savage attack on Black Cat, a Spider-Man villain who is also sometimes an ally. Spider-Man took his anger out on Doc Ock so savagely that Octavius was never really the same.
Almost Married Aunt May
One of the stranger episodes in Doctor Octopus' long history with Spider-Man came in the 70s. Despite being the target of Doc Ock's schemes, Aunt May eventually took a liking to him.
He also became fond of her and the two very nearly married. May was the target of other supervillains, like the Vulture, who kidnapped another love interest of hers, Nathan Lubensky. Lubensky died of a heart attack after his ordeal and May refused to forgive Adrian Toomes despite his deep regret.
Anti-Hero
His experience with Aunt May was an early indicator that Doctor Octopus isn't a simple villain. His conscience sometimes breaks through. Over the years, he would display confusing degrees of consideration toward others. Perhaps the best example came during the Clone Saga, a 90s Spider-Man storyline generally disliked by fans.
The Vulture poisoned Spider-Man with a deadly virus during the event and Doctor Octopus saved him if only to be the one to actually kill the Wall-Crawler.
The Superior Spider-Man
Doctor Octopus did become a superhero of sorts in one of the biggest twists in the comics. The ailing Octavius swapped minds with Peter Parker, trapping the younger man in his frail body which then died.
Octavius assumed the identity of Parker and Spider-Man, becoming the Superior Spider-Man. Octavius cosplayed as Spidey for years, acting as a hero in ways he never really expected. Everything was eventually put right, though Octavius never stopped trying to destroy Spider-Man completely.
Spider-Verse
Alfred Molina's Doctor Octopus is one of Jamie Foxx's Electro from Amazing Spider-Man 2. This multiverse concept is not new to Spider-Man or Doctor Octopus at all. He has many different versions in many different realities in the comic books.
One of the most significant is the Ultimate Doctor Octopus, who had a clear role in informing Molina's version of the character. This version, from Earth-1610, was more of a mentor to Spider-Man before becoming one of his greatest enemies.
Evolving Armature
The armature of Doctor Octopus, one of the most iconic Marvel weapons, has evolved quite a bit over the years. It was originally a harness that Doc Ock wore and the four arms were physically manipulated.
He later adopted a suit of armor to protect him from his epic battles with Spider-Man (and old age). Others imitated or outright stole his designs, like Doctor Octopus III. Octavius also gained telepathic control of his varied mechanical arms after an experiment gone wrong.
Octobots
Another weapon in Doctor Octopus' arsenal is the Octobot. This scary drone is not unlike the many drones of Ultron, the main villain of Avengers: Age Of Ultron (who the film didn't quite get right). This multi-tentacled orb-like robot swarms its prey and applies the same technology as Doc Ock's arms.
He also controls them psychokinetically as he does his primary arms, giving him mental control over a vast army. These terrors come in all kinds of sizes large and small, with major variations being the Spider-Slayers and Spider-Bots.