There have been no concrete plot details for "The Amazing Spider-Man 3" yet, but fans are already speculating about which of the villains in the popular comic book will appear in the movie adaptation. According to Youth Health Mag, hints about who might be Spider-Man's future opponents were shown during the climax of "The Amazing Spider-Man 2."

ComicBook.com reports that the Easter egg images appeared to be teasing various members of the Sinister Six, which included Doctor Octopus, Electro, Sandman, Vulture, Kraven the Hunter, and Mysterio. Listed below is what you all need to know about the possible villains that fans are interested to see in the upcoming "Spider-Man" sequel.

Kraven the Hunter

Out of all the characters rumored to be appearing in the film, Kraven the Hunter seems to be the most possible to make an appearance. "The Amazing Spider-Man 2" director Marc Webb revealed in a ComicBook.com interview that he would be most interested in bringing Kraven the Hunter to life on the big screen.

"I like the idea of Kraven. The Vulture. Ock. I always thought the idea of Mysterio was interesting. Maybe Scorpion. But really, Kraven I think is kind of interesting," Webb told ComicBook.com.

The news outlet reports that Kraven is "a classic Spider-Man villain" and a "founding member of the Sinister Six." The character, created by Stan Lee and Steve Ditko, is reportedly a descendant of Russian nobility who was forced to emigrate to the United States in 1917 after the February Revolution. "Kraven became an obsessive big game hunter and, after mastering the sport, decided to hunt Spider-Man to prove that he was the world's greatest hunter," ComicBook.com notes.

Kraven's most noteworthy story is "Kraven's Last Hunt," by J. M. DeMatteis, Mike Zeck, and Bob McLeod. The story features his one last attempt at defeating his foe Spider-Man before succumbing to his death. "Kraven's Last Hunt" also revealed "much of Kraven's back-story and added layers of depth to what was previously a pretty gimmicky villain."

Mysterio

Webb also expressed interest in casting Mysterio, another supervillain from the Spider-Man comics universe. According to the director, they already got a company to start designing the elements and hardware of the Sinister Six.

The director told ComicBook.com, "So we've got this company called Blur, Tim Miller to start designing the elements of the Sinister Six, the hardware of the Sinister Six, which is something that's hinted at in the movie."

"It's tricky, because we're not exactly sure if all those people are going to be in the Sinister Six or even in the next movie. Like the Mysterio mask, I just think looks really cool. And I love Mysterio, but we haven't all agreed on it, so but I just forced it in because I thought it looked cool," Webb added.

Venom

Venom has also drawn the attention of the fans. According to International Business Times, the character is "a symbiote that needs a host to survive and has dawned many faces in the Marvel comic universe." The villain attached itself to Peter Parker, Eddie Brock, Flash Thompson, and Harry Osborn but was most venomous while in the body of Brock. It is unknown which of the faces will be used as Venom in the "Spider-Man" sequel.

Rhino

Although not a part of the Sinister Six, fans are also expecting to see Rhino. Collider reports that Paul Giamatti is confirmed to play the villain a.k.a. Aleksei Sytsevich in a multi-picture deal that includes the third "Spider-Man" movie.

The character is a member of the Russian Mafia, as stated by Marvel.com. Desiring immense wealth and power, he "underwent a life-threatening series of chemical and radiation treatments to transform him after several months into the superhumanly strong agent for a collective of professional spies--in part, to support his family." This treatment led to "Aleksei's powerful armor permanently bonded to his form," Marvel.com adds.

"The Amazing Spider-Man 3" is scheduled for release in 2018 with no official date yet, MStarz reports.