2.) He knows what awaits him after death, and because of this he so frantically seeks to escape it. His peculiar looks - the same look that his entire family had - come from a pact so vile and unspeakable that Orochimaru lost control of himself and covered half of the text in vomit out of sheer, undescribable horror. After all, how much would you like to know that your soul belongs to the all-devouring eight-tailed and equally eight-headed Orochi, from birth on?
3.) Jiraiya was the dancer, Tsunade was the singer and Orochimaru was the musician. Where Jiraiya managed to focus the attention of everyone on his magnificent twists and twirls and Tsunade could all but seduce people with her voice alone, Orochimaru prides himself on the ability to make people cry with emotion with nothing but his music.
4.) Without his assistance early on their way to becoming Sannin, Tsunade would have never become the unsurpassed medical genius that she is. If not for his callously arrogant taunting of Jiraiya, the man would never have found the burning urge to prove something to everyone who'd listen long enough to him to prove something. And while Orochimaru likes to think that the others didn't have anything to contribute to his magnificence, deep down he knows better.
5.) Orochimaru's soul is a virgin. He isn't sure about the bodies he has inhabited ever since, but he himself has never - and will not ever - be a player in the never-ending mating game. He will not make a child suffer the curse of the Orochi if he can prevent it.
6.) He regards surgery as a form of art, not unlike Deidara does with explosions. Usually with the same results, too, because he cares little whether the latest test subject lives to tell the tale or not. It is because of this that he gets along so well with Sasori, because a surgeon never knows all tricks of the trade and sharing most certainly helps to improve ones performance.
7.) If blackmailed into revealing it, he'd admit to missing the Good Old Times in Konoha, before the Hokage mess and the bloody experiments. He has gained a way to escape from the fate that claimed all of his family though, and he realises that such a thing must surely have a price. Still, better a traitor in life than damned in eternity.
8.) While they are fearsome, insane, powerful, freaks of nature or a combination thereof, his former colleagues in the Akatsuki know little of genetic security. He has enough material - from each of them - to, at the very least, create a sibling to them. In some cases, he has enough to outright clone them, but that is an area where not even Orochimaru dares to thread.
9.) He fears death, and because of this he trained himself to become faster, stronger, quicker, more powerful than anyone else. It was not until he was at his absolute best that, for the first time, he considered that no matter how powerful he got to be, someone would be more powerful than him. It was after this conclusion that he began to train himself to be better, not merely more powerful. It is because of this that he has survived so much for so long, because with a few exceptions, he is the best at everything. Everything but being human.
10.) He is vain, more so than even Tsunade and Jiraiya combined, and takes great care to make the impression his clothes give have a lasting effect. Of course, as with anything else, even this habit has a reason. After all, how many people will take their enemy seriously if he runs around with a barely covered chest and wearing a big. purple bowed ribbon over their ass? More than once their ridiculous appearance has helped the Sound shinobi achieve victory... at the cost, of course, of wearing a purple ass-bow.
11.) Orochimaru considers himself to be genuinely evil. He has accepted and embraced the fact that he will betray everything and everyone, that he will do anything to avoid death. There is no price too great to avoid eternal damnation, and this is his life, the never-ending attempt at avoiding the fate of every man.
12.) He hates, nay, despises the very notion of a pre-set destiny. He is his own man, shaping his own future with his every action. He refuses to believe that some supernatural entity can set the path of one's future - an understandable reaction given what he knows his fate is. Orochimaru is, in this regard, wiser than most, appreciating the difference between fate and destiny.
13.) The Kusanagi is more than a tool to him, it is an extension of himself. When he watches Uchiha Sasuke clumsily fumbling around with the very blade that moves like quicksilver while in his own hands, he doesn't know whether to laugh at or mock the "prodigy". In addition to his unparalleled and unheard-of control of his Kusanagi, he'll never forget the look on the faces of The Team when he first dislodged the thing from his mouth. Truly, those were the times.
14.) When it comes to creating, analyzing and dissecting jutsu of all kinds, he is the greatest genius in the history of the Elemental Countries. Not even the computer-like mind of Uchiha Itachi can compete with him on this level, and Orochimaru knows this. It is because of this that no-one with the exception of his former teammates, his teacher and maybe, just maybe taijutsu-masters like Maito Gai can stand up to him. Unless they wish to end up facing an enemy that can pick apart all their little tricks within seconds and explout their weaknesses without mercy.
15.) He got his place amongst the Akatsuki by entering their hideout during one of the - at that time - semiannual meetings and dissolving the first idiot that tried to jump him with one of the most unrelentingly cruel acid techniques he knew. It left an impression, too, both in the minds of the other Akatsuki and on the ground - the bent and twisted skeleton remains, to this day, fused to the stone as a warning that not every weary-looking traveller is easy prey.
16.) He spent a regular run in the Konoha ANBU, and even to this day, when he performs unspeakable experiments on other sentient beings he is sure that no matter what he does and to whom, it will not ever be as terrible, inhuman and cruel. After all, he gifts only the best and the brightest with his cursed seal and doesn't murder the righteous and innocent for money alone.
17.) Orochimaru has lied to Hyuuga and gotten away with it. He has sparred with Uchiha and preserved his techniques. He has eluded Inuzuka trackers and Aburame assassins. He fears no clan in Konoha, living or dead, because he knows that they can not match him. He is only wary of those no-named students, those without a grand past to their names, because he knows as one of their kind himself that the greatest of the great oftentimes start out at rock bottom.
18.) Uchiha Itachi is by far the worst opponent Orochimaru has encountered in battle in his overly long life so far, and there is good reason to it. The snake summoner fights by showering his enemies with the deadliest of ninjutsu known to man, while at the same time picking their techniques apart and demolishing them through using the flaws of these techniques. Unfortunately, Itachi does the same, and with the added benefit of the Sharingan doing things the old fashioned way - stabbing him with the Kusanagi until he stops moving - isn't an option either.
19.) It was he who taught Anko everything she knows about tea - how to enjoy it, how to brew it, how to properly serve it. Orochimaru has, under three different names, prepared tea for every daimyo of the elemental countries and considers this his greatest success of all things not related to the shinobi world.
20.) He knows Kabuto better than Kabuto knows himself. While the silver-haired sadist believes that he owes allegiance to no-one, that he is free to do as he pleases and betray whomever he wants, Orochimaru knows that Kabuto is bound by his past as surely as if he were in irons. Kabuto will forever make himself feel inferior because he lacks a past and constantly betrays and double-crosses his own future.
21.) Orochimaru dies unrepentant. He had gone so far as to taint his very soul with the darkest of techniques to avoid it, but as life bleeds out of him nonetheless, he is content with the knowledge that his murderer will find no peace in life or death. The Cursed Seal was more than just a shortcut to power, it was a funnel for the very curse that once plagued his own soul and blood. Uchiha Sasuke will find that even if he restores his clan, there will be no peace in life or death for him or them.
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All of this was written before the sad, sad mess that the revelation of our favorite hero's parentage and the real antagonist have wrought. I reject reality and canon and substitute it with my own.