Anyone?

My choice would be...

Mysterio: His special effects are amazing, he would offer the other villains an easy chance to surprise anyone.
Super-Skrull: He has all of the Fantastic Four's power, he is very powerful.
Red Skull: He would be the leader. He is a genius strategist and can come up with really evil pan.
Avalanche: With his ability to create earthquakes he can easily ruin an enemy's formation.
Juggernaut: He is fast, powerful, and nearly unstoppable.
Hydro-Man: Every super-villain group needs someone able to alter their shape

My Sinister Six is all Marvel Villains who aren't all powerful.  

"My choice would be...

Mysterio: His special effects are amazing, he would offer the other villains an easy chance to surprise anyone.
Super-Skrull: He has all of the Fantastic Four's power, he is very powerful.
Red Skull: He would be the leader. He is a genius strategist and can come up with really evil pan.Avalanche: With his ability to create earthquakes he can easily ruin an enemy's formation. Juggernaut: He is fast, powerful, and nearly unstoppable.Hydro-Man: Every super-villain group needs someone able to alter their shapeMy Sinister Six is all Marvel Villains who aren't all powerful.   "

"My choice would be...

Mysterio: His special effects are amazing, he would offer the other villains an easy chance to surprise anyone.
Super-Skrull: He has all of the Fantastic Four's power, he is very powerful.
Red Skull: He would be the leader. He is a genius strategist and can come up with really evil pan.Avalanche: With his ability to create earthquakes he can easily ruin an enemy's formation. Juggernaut: He is fast, powerful, and nearly unstoppable.Hydro-Man: Every super-villain group needs someone able to alter their shapeMy Sinister Six is all Marvel Villains who aren't all powerful.   "

" @Omega-Mekix said:

"My choice would be...

Mysterio: His special effects are amazing, he would offer the other villains an easy chance to surprise anyone.
Super-Skrull: He has all of the Fantastic Four's power, he is very powerful.
Red Skull: He would be the leader. He is a genius strategist and can come up with really evil pan.Avalanche: With his ability to create earthquakes he can easily ruin an enemy's formation. Juggernaut: He is fast, powerful, and nearly unstoppable.Hydro-Man: Every super-villain group needs someone able to alter their shapeMy Sinister Six is all Marvel Villains who aren't all powerful.   "

Cool, sounds more like the Masters of Evil "

Green Goblin
Grey Goblin
Proto-Goblin
Hobgoblin
Demogoblin
Menace

Gallery

1. The Hood
2. Mr. Fear
3. Doc Ock
4. Sandman
5. Scorpion (Gargan)
6. Crossbones

How about a new Sinister Seven:
Leader: Hobgoblin (Rodrick Kingsley)
Ven-orpion
A new Mysterio
Moribus
Menace
Electro
Vulture (Adrian Toolmes)

"Green Goblin
Grey Goblin
Proto-Goblin
Hobgoblin
Demogoblin
Menace

Gallery

"

"Green Goblin
Grey Goblin
Proto-Goblin
Hobgoblin
Demogoblin
Menace

Gallery

"

"@KillerZ said:

"Green Goblin
Grey Goblin
Proto-Goblin
Hobgoblin
Demogoblin
Menace

Gallery

"

Lol...it's like the Sinister Goblins"

My new Sinister Six is made of those who have the potential to become unstoppable.
 
Spot: Teleportation will help the team so much
Toad: Extremely agile and under minded, he could become a huge threat
Tombstone: Team leader and excellent fighter.
Domino: Good luck, good weapons.
SuperSkrull: As said earlier, he has the fantasic four's powers
Mysterio: The team could use someone who has the skills to deceive the enemies.

• Doctor Octopus, a science genius and the leader of the Six
  
• Mysterio, powerfull illusions and holograms used for diversions and tricks.
  
• Omega Red, he can disorient opponents while fighting them. He's also an expert fighter.
• Shocker, the long distance fighter of the team.
• Sandman, super strong and can turn into any form of sand.
• Super-Skrull, but with the combined powers of Wolverine, Colossus, Cyclops and Hank Pym
  

" Is this limited to Spider-Man villains? "

" @k4tzm4n said:

" Is this limited to Spider-Man villains? "

I don't think so "

Well, in that case...  (unlike some, im not looking to make an entirely unstoppable team here, lol)
 
Leader: Sabretooth.  Despite people thinking he's a savage idiot, he's proven he's rather bright (hacking into shield CPU) and tactical.  His experience and senses allow him to give the team an advantage as well.  He's shown what he has to lead a group of villains before (mauraders, identity disc) 
Tank: Omega Red.  Durable, strong, tactical, smart, skilled.  IMO, that's what a "tank" character needs to be. 
Stealth: Kraven.  The guy is able to track Spider-Man...Someone with a freaking radar warning them of danger.  If detected, he has the skill to retreat or even hold his own against some.  His poisons would be a great addition as well.  
Rage:  Bullseye.  The most accurate man in the marvel u.  Being told not to hold back, he can dish out some major damage. 
Variety: Venom (Brock). Can play as a tank (durable, strong), range (webbing), stealth (cloaking)...However, makes for a very sub-par leader .

Research: Doctor Octopus (adamantium) Despite having a fair amount of tactical people, there's no one that really has the intellect to come up with a "bigger plan" or obtain better tech. 

"Leader: Mr. Negative
Members:
Vulture(BND)Spot(BND)Hammerhead(BND)Kraven(BND)Freak"

• Norman Osborn (Green Goblin): Leader
• Red Vulture
• Electro
• Kraven (Ana)
• Rhino
• Venom (Mac)
  

• Vulture (LEADER)
• Lizard
• Shocker
• Electro
• Hydro-Man
• Rhino

• Green Goblin (Norman) (leader)
• Dr. Octopus
• Hydro Man
• Electro
• Mysterio
• Scorpion

Leader: Kingpin

Vulture: Field Leader

Kraven

Shocker

Electro

Scorpion

Big reveal: Kingpin isn't part of the Six. they just work for him. CARNAGE is the real sixth member.