All you need to be a supervillain is:
1) A cat
2) An underground/undersea/dormant volcano base
3) Style
4) The will to do ANYTHING to achieve your goals, no matter the cost
Being a whacko IMO, disqualifies you from being a supervillain, as that just makes you a whacko.
EDIT: 5) A legitimate public face is always a good bonus, as generally people won't know you're a supervillain until it WAY too late! 
@FloatingFatMan
Do not go gentle into that good night.
Rage, rage against the dying of the light.
"The total compulsive inability to resist a detailed monologue and rundown of your secret plans in front of your nemesis when you think your victory is assured!" ... has to be the most hilarous, lovable and well-known attribute of any self-respecting Super-Villain. 
What makes a great super-villain:
1. Charisma. You gotta talk the talk to walk the walk, to be able to pull of meanacing, intimidating, flattery, charming, negotiations and all those other things to get to your goal.
2. Leadership. You are in control, you need to let people know this, and make them loyal to you. Make sure your henchmen are motivated through special fun days, job perks and comprehensive medical insurance.
3. Know-how. You need to be good at what you do. Half-[censored] jobs won't cut it here. You have to think on your feet, be able to adjust to situations, and to outwit those who'll try and stop you.
4. Willpower. You have your goals. You need to be able to go through with them as much as possible, not bowing to no one or conceeding defeat to anyone. Unless it goes with point 5.
5. Cunning. Stealth. Deception. Ruses. Counter attacks. Feints. Subversion. These are all valid weapons and tactics. Use them wisely, lure your foes off guard. And take them out.
6. No elaborate plots. No sharks with frickin' lasers. If someone stands in your way, dispose of them simply and quickly. Sure, have style in your work, but don't be so theatrical.
7. Resources. Accumilate. Acquire. Spread your influence through material possessions. Get the people to love and rever you, or fear you. Don't get them to hate you. That leads to weaknesses and downfall. If you can accomplish your goals with the people on your side, you have a secure power base.
8. Contingency. Have back up plans for your back up plans. Make every defeat against you just lead to something else. Every cloud has a silver lining, and good can come out of bad. Be like the bamboo, and flow with the wind when needed. WIth a good back up foundation, you may find even more profit and success.
9. Morality. Goals. Ideals. You aren't doing things to be evil for the sake of it. Heck, you aren't even evil. Only those who don't understand, who fear change, who prefer the status quo and live in their happy little bubble of shared norms and values call you evil. Progression comes with change, people fear change. So people fear you. Do what you must to get the people on your side, when your utopia arrives, you will have cast their minds ready to accept it too.
10. And the most important thing about being a successful super-villain?
For most of the time, people won't even suspect you are evil at all.
... 
I used to get a lot of positive comments about Lunk before he went back to hero-side. But then he was more of an anti-hero than villain, but there was still several traits that stand out.
1) Twisted logic and morality: the self justification of acts of evil. "Muhahahah! im evil!" gets boring fast. In a good villain's mind he's right, and the hero is wrong.
(lunk example: EVIL's kidnap plot for an unidentified group of heroes in the Isles turns out to include a personal friend (Coile), who is then strapped to a bed for 3 days, yet still chatted to as if nothing is wrong. but hey, thats business.)
2) Not just all hot air. It's all fine and good throwing around threats about feeding to shark's, but its another thing entirely to carry it through.
(the entire destruction of an African town and hundreds of casualties amongst the residents whilst breaking into the national reserve)
3) Presence: a good villain inspires fear and hate. They have to be suitable enough for a hero to 'hero' against. Captain Elasto may look dandy in his rubber suit, but if he's as intimidating as a wet cloth, and just as big a threat, he's not getting very far. You have to love to hate them.
(during the Bonefire Havok plot, there was a moment where Lunk confronted the Havok brothers, [censored] off about paying for a failed assassination attempt on Bonefire, and threatening the pair.
It was described OOC by one of the brothers players as "causing his nuts to shrivel" in fear in RL" 
)
A great super-villain has to have a twisted reason for what they do or no reason at all. You are evil because, I dunno, a hero stole your girlfriend and you're now trying to kill all the heroes in hope that you'll get a girlfriend (Bad example, I know ), or that they do what they do because they think they should simply because they can.
For example, my recently deceased villain Spruk killed people because he thought that because he had powers, he had an authority over those weaker than him, and thus could do what he wanted to them. And my current main villain, Lord Darvek, kills/destroys because it's what he does, it's what he is, he kills because it's what he's there for, nothing more nothing less.
I am the Blaster, I have filled the role of Tank, Controller and Defender
Sometimes all at once.
Union EU player! Pip pip, tally ho, top hats and tea etc etc
[ QUOTE ]
You are evil because, I dunno, a hero stole your girlfriend and you're now trying to kill all the heroes in hope that you'll get a girlfriend (Bad example, I know
[/ QUOTE ]
That's scarily similar to the origin of XV's all consuming hatred of all that is good and pure.
I think you have to be narcissistic, insensitive, systematic, charismatic and most of all fearless.
He will honor his words; he will definitely carry out his actions. What he promises he will fulfill. He does not care about his bodily self, putting his life and death aside to come forward for another's troubled besiegement. He does not boast about his ability, or shamelessly extol his own virtues. - Sima Qian.
The greatest villains are those one loves to hate.
There are two main paths that lead to such a dark love.
The first is to be iconic. This often takes originality, and always comes with a very distinct, moving and memorable appearance. These villains make you shudder a litle at first sight.
The second path is to be a villain one can empathise with. You can see a certain logic and sense to this villain, and could almost feel you could join him.
There are even examples of those who take both paths togethe, though rare. One would surely be Darth Vader, who after all these years is still one of the mst iconic super-villains of fiction.
His appearance is certainly iconic, not just in one of the most stunning designs of costume, with that gleaming black helmet that evokes both the human skull, and the infamous Nazi helmets of WW2, but also in the artificial forced breathing, and the mechanical edged rich voice.
One can see all too easily how his desire for power, originally desired for noble puposes, brought him down a dark path and created a monster. But a monster one can feel empathy for, and certainly respect.
http://www.savecoh.com/
Simpletons,
I, Hatesman, wish to uncover the pathetic drivel that you pass off as concious thought, in an attempt to improve and enhance the services provided by the Rogue Isle's Super-Villain community. Your only options are Compliance or Annihilation!!
OOC:
No! You're not simpletons! Haha, don't listen to Hates. =P
So,
At the start of my RP Villain Group the Terra Liberation Front I began writing a guide called "A Guide to Super-Villainy" which so far has one chapter describing how Super-Villains need a theme. Due to my procrastination, I decided that this guide was unnecessary and put it to one side.
Now I've picked it up again and I'm back with it, and while I think I do have an idea as to what makes a Great Super-Villain, I'd like to know what your opinions are. After all, to Role-Play a Super-Villain in City of Villains is to often try to cater to an audience of highly critical, egotistical (read: 'Exceptionally Brilliant') actors and actresses, who probably know what makes a great character already, and I think a lot of roleplayers stay away from playing Super-Villains because they seem to be a shallow option next to the mighty Super-Hero, who is the master of their own story.
So far my list is as follows:
1. Theme - Every Great Super-Villain needs a theme, just being evil is not enough for greatness, anyone can act and think they're Evil even Heroes, but only the Great Super-Villains will bear a signature theme.
2. Derranged Personality - I think that all Great Super-Villains need a derranged personality. Be it a Sociopathic nut-job, a crazed serial killer, or insane scientist. This should stem from a single point in their life, perhaps when they gained their powers, from being picked on in school, or simply being born to Vampires. Once again it's not enough for a villain simply to be Evil in my book for the sake of being Evil. Being bad, just because they can be, isn't a good enough excuse, that's how Henchmen get their jobs, it's not how Masterminds should do things.
So I put to you, the humble Roleplayer...
What Makes a Great Super-Villain?
It takes Chaos to move the world to Action.