When he is in good mood Felix has an overall very noble and heroic personality, he is selfless and kind-hearted, and deeply values the safety of everyone and his friends. Because of this, he is seen by most other characters in the show as a dependable person they can always trust.

Felix is also usually depicted as being serious, calm and clear-minded even in some situations. Due to this he rarely acts on impulse and usually thinks things through before he make a action, always trying to stay one step ahead of his enemies in his mind in order to devise his strategies. He is also very selfless, and is hesitant to put the safety of his friends, or anyone else at risk.

Felix gets annoyed at those who are greedy, cowards, cheaters and discriminate others, so much so that he doesn't consider them deserving of calling themselves braver and civilized even consider them a pathetic low life. However, his opinion can change if such people really reform but he still he doesn't let his guard down.

Felix has had a fear of flying cockroach, he is very dedicated, and shows a great sense of conviction towards his work and action, despite his lack of support and he is also cautious about every action he makes. His voice tone changes between mood on his calm mood his voice becomes low and he talks very slowly as if he has found an inner peace but he sometime speak has medium-pitched voice and his talking speed is normal trying to talk calmly to someone at times.

But there are times where he talks angrily or impatiently when he is angry. It is likely his tone was driven by a desire to keep himself calm, however his anger and frustration sometimes breaks through him. Felix is often described by some of his friends as a very serious and devoted to his life and action. Felix is mostly calm, solemn and level headed, because he conceals his true feelings.

"What will happen to this world if humans continue to breed and continue have conflict to each others? Don't you see? Humans have set themselves upon the path to inevitable destruction."

Because of his hate for humanity and his self-imposed strict discipline, Felix is rather anti-social, shy and withdrawn, causing him to be wary and curt towards people that he does not know, and perhaps as a result of his difficult life, Felix is a cold individual and after repeated betrayals and mishaps by many people.

Felix's worldview became increasingly cynical and nihilistic, and this attitude made Felix develop a habit of trying to do thing on his own, becoming defensive and even aggressive when help was offered. Due to the isolated lifestyle that had dominated the most of her life, Felix is often lacking in social skills, often finding it hard to open up to and talk to people, and he is very focused when it comes to his goals and can be quite stubborn once he has put his mind onto something, causing he to become rough, impatient and sometimes even aggressive to almost anyone who ends up getting in his way.

Felix is seem to faces every situation with a 'John McClane' type wit and a very dark sense of humor which joins his nothing-to-lose demeanor. Felix has a sense of describing his actions. He does not believe his doings are heroic and yet he doesn't believes he should be punished for his actions with few exception.

Along with his dark sense of humor, he is also very morbid, and he tends to make jokes even in the face of trouble as dry jokes. Felix pursues his enemies with deep perseverance, some even say fanatically as no matter how difficult injure it may look, how injure he might be or how many laws he might be breaking, when he sets his sights on his target, he refuses to let go of them.

If it means killing all the people that happen to block his way or even wipe out human population, whatever it might be that impedes serving his revenge Felix is not hesitant to overcome. This is possibly due to the fact that Felix no longer have compassion towards his fellow people on the contrary he often despise them.

And his disinterest in close relations probably results from his hate for humanity, and his intention to wipe out humanity for the face of Earth is to put an end to free people for this curse world once and for all, and won lots of enemies through his actions. His reason to despises humanity it's due for the their action such as discrimination, oppression, and terrible excuse, and it is mostly this that motivates him to hate humanity.

Despite this he seems at times to display a certain sense of honor, even with his dark and melancholic perception of the world around him. Felix is a truly good person who do his best to avoids problem for people own safety. He is also hate excuse that he find stupid and so he wouldn't accept anyone excuse for their action such when someone use the excuse "it's just business".