As a human, Klaus was treated very poorly by Mikael, always getting ill-treated and punished for things that others were guilty of as well (like when Elijah and him were sword-fighting (playing) Mikael punished and yelled at Klaus, rather than at Elijah, the older brother - who was also an active participant and having fun as well).
Obviously, he was not the perfect child, a daredevil perhaps seeing as to how he went and watched the wolves transform with Henrik - but also, where were the parents when they snuck out? Anyhow, people do things that are provocative and dangerous, things they deem interesting and daring all the time, especially men (I have friends that are adrenaline junkies, mainly they are males).
As a human, he did not kill anyone, or else his werewolf side would have been triggered. And he may not have killed anyone in his life if they had not become vampires.
When Mikael drove his sword through their hearts, the children were confused, and what was Klaus' reaction at first? he was reassuring Rebekah that everything will be all right, and went in to protect her even though he knew how Mikael would react towards him. Also, I shall add the fact that Klaus had no say in what was to happen to him, he didn't choose to become a vampire.
After becoming vampires, Klaus made his first human kill (maybe accidentally, maybe not, but that is not the point) and thus triggered his werewolf gene - showing that he was not the son of Mikael. Here he became known to Mikael, who always hated him, as an abomination, a bastard...Mikael killed Klaus' bio-dad and half the village, very awesome, killing half of the bio-family. I don't think Klaus admired this, umm...because it showed just how much Mikael hated everything Klaus stood for (indirectly, may I add).
What happens to him then? Hmmm...his mother puts a curse on him and assumingly sacrifices Tatia, the girl he loved, in order to make his werewolf side dormant, thus him not being able to maximize his full, natural potential. So I understand why he killed Ester, in a moment of rage and hurt. He thought that Ester hated him, for a thousand years he thought she hated him. In 3x05 he told Rebekah "Well, you know how much the Original witch hated me"...
Those emotions never die down, not ever. Knowing that you were cursed, and that your own mother did this, sacrificing the woman you loved (or used to love) and making her doppelgangers reappear every 500 years in order to break this curse (where he would have to kill said doppelganger) is actually sickening. Klaus' views of trust and love were distorted for all time, he felt alone and unwanted, an abomination. That is why he held on to his siblings like that...and mind you, his emotions as a vampire are heightened, as is with every vampire. Klaus has no tolerance for those who disappoint him.
Now, I am going to say though, that treating your siblings like that is completely and utterly wrong. Daggering them for hundreds of years so you would not have to face them going away and disagreeing with you is wrong. I think he deserved, very much so, what happened to him in 3x13. He had his siblings on his side, and he drove them away from himself because of his grand sense of abandonment, he was and is paranoid about this.
I would say that Klaus does have an inflated ego, but I would say that a lot of vampires on the show have that as well, just not as pronounced as Klaus'. I think he yearns for love and acceptance, but goes about it in a completely wrong way, because his sense of love and trust are distorted. He cannot bring himself to show some emotions that I believe, he has in himself. I believe he does and is able to love others, but he has inhibitions that he should rid himself of first.
გენიალური პოსტი კლაუსზე, მეზარებოდა თარგმნა, ვინც გაიგებთ გიხაროდეთ
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ვამპირის დღიურები/The vampire diaries VOL VIII, Season 3
