Real name: Eddie Brock
Origins: Came into existence when the symbiote once attached to Spider-Man bonded with Brock.
Powers: Shares many with Spider-Man as the symbiote developed while attached to the webslinger, which means Venom possesses superhuman strength, incredible agility and wall crawling ability. Venom can animate any part of the suit so he lashes out with tentacle-like appendages.
Motivation: Both Eddie Brock and the symbiote have a real problem with Peter Parker/Spider-Man, and they take great pleasure in tormenting him.
Weaknesses: Is vulnerable to sonic and thermal attacks.
Green Goblin 2
Real name: Harry Osborne (we assume)
Origins: This is being kept under wraps for the moment, but given Harry’s discovery of his father’s Green Goblin gear at the end of Spider-Man 2, we reckon he utilizes it all to get his revenge on Peter Parker and Spider-Man, who he knows killed his dad. (To be fair to Spider-Man, the Green Goblin was obviously insane). In the comics, Harry also assumed his late father’s role as the Green Goblin, and another character, Roderick Kingsley, adopted the Green Goblin’s modus operandi as his own and became the Hobgoblin.
Powers: Should Harry take the Green Goblin formula his dad created, he’ll gain super-strength. He’s also got a sweet Goblin Glider, Pumpkin Bombs and other assorted weapons.
Motivation: To take revenge on Spider-Man for the death of his father.
Weaknesses: He’s tough and strong, but he’s just some guy on a flying skateboard.
Real name: Flint Marko
Origins: In the comics Marko escapes from prison, fatefully hiding in a nuclear testing area where a radioactive blast fuses him with the sand beneath his feet. In the film Marko is on the run from police and finds himself in a particle physics laboratory where he gets trapped in some apparatus that turns him into living sand.
Powers: As the name suggests he is completely made of sand which he can shape into any form - hard, gritty and uh… sandy. He has superhuman strength that is in excess of Spider-Man. He can manipulate and merge with natural deposits of sand (beaches, deserts) increasing his size and strength.
Motivation: It turns out that he has connections with the criminal that killed Peter Parker’s Uncle Ben or might have even been Ben’s murderer, so it’s Spider-Man that’s after him.
Weaknesses: Very few as he can continually reform. He can turn to glass if exposed to extreme heat, and in the comics he suffered from a bite by Venom. (Also, Sandman once accidentally combined with Hydro-Man, creating a huge mud monster. The incident left both psychologically scarred).