Blut und Ehre

The Hero Killer’s fight with Deku, Todoroki and Iida demonstrated that his Quirk, Bloodcurdle is most effective against those with Type B blood - like the hero he attacked, Native - and the least effective against those with Type O blood, like Deku. 

This fits Stain’s ideology perfectly: his Quirk is most effective against the kind of people he wants to purge from society (selfish and lazy heroes who do or don’t do their work for money or fame) and least effective against the kind of people he wants to see become true heroes (strong-willed, agreeable/kind individuals who save people selflessly like Deku).

The irony is that Stain himself also has type B blood. Whether this makes Stain a hypocrite, a self-hating or self-aware and introspective person is up for debate. Here I’m only going to analyse the specific traits that are attributed to Type B individuals and see how they reveal themselves in Stain.

Let’s start with the best.

Best traits

Passionate

Seriously? You wouldn’t have Stain if he didn’t have passion! Passion runs through him like a stick of rock. It encases his unflinching moral code and drives him every waking moment of the day. It’s what makes his charisma so powerful, even to complete strangers.

His passion remains a product of his steadfast will, morals and idealism. Before he walked the path of a vigilante and serial killer, Stain was more than likely a sincere, self-sacrificing and highly moral individual who would aspire to emulate the just and selfless heroics of All-Might. He must have exuded the same sincere passion when he made his soapbox speeches, only to be entirely ignored or rejected. Currently a not so insignificant portion of his passion is likely fueled by the despair he felt then.

You could argue that Stain is so devoted to the example set by heroes like All-Might, the ideal hero, that he is willing to destroy himself for the sake of the greater good. From the apparent dissociative attitude towards his alter-ego Stendhal in the Illegals spin-off, where Stain refuses to view himself and the blood-stained killer as the same person, and unyielding commitment to his reasons for killing as Stain - taking every opportunity given to him to justify his methods to others - Stain seems to be fighting a constant battle against himself. 

The notion of killing the very people whom he had once idolised and wished to become, who he would most likely be far happier being right now, may account for his crazed tenacity and bloodlust. By convincing himself it is the only way to bring about change, Stain has trapped himself in a life of killing. The young man who onced dreamed of being a hero has become a murderer  - no amount of conviction can wipe away the inherent despair, rage and self-destruction that entails.

Stain is not your typical maniacal villain, who derives happiness and satisfaction from killing. In fact, the only time he ever really smiles is when he is confronted by Deku in the alley, and perceives All-Might’s selfless heroism in him. Though the smile appears crazed, I believe it was genuine. Stain has dedicated at least twenty years of his life to bringing about a world where true, noble heroes like Deku exist. Seeing one in front of him, believing most others are nothing but fakes, must have elated him. 

Not only does he see Deku as someone worthy of being kept alive, but Stain actively goes out of his way to save Deku when he could have easily escaped.

Active

If you dedicate your teenage years to making speeches in the name of reforming what you believe to be a corrupt society, crying out for a revival of heroics and return to a more just and selfless world, then dedicate your twenties and thirties to making that a reality through action, researching and disciplining his body and mind through self-study in order to achieve this... you are not lazy by any stretch of the imagination.

This man has been nothing but active for his entire thirty-one years of living, for better or worse. Since childhood he has always set himself a goal and done whatever he thought was best to achieve it. Even his enemies comments on his drive. It is unfortunate that this extreme drive and tenacity was poured into become a murderer, however.

Creative

This trait is evidenced by Stain’s fighting style. Though he is not as clever as Deku or powerful as other heroes, he is a thinker. He analyses Deku’s movements during their fight, comes up with a strategy to get close to Shota and paralyse him all in the space of a few seconds, and utilises his weapons in a multitude of different and inventive ways. His weapons are all specially utilised to facilitate and accentuate the effectiveness of his Quirk.

Even when severely injured and having only just come to after being knocked out, Stain is able to act to save Deku from the clutches of a Nomu when nobody else can even move. He thinks outside the box, using his Quirk resourcefully, albeit creepily, by licking the blood off a Pro Hero’s cheek in order to paralyse the Nomu before charging in for the kill.

His creativity in battle is lost, however, when he is pushed too far against the wall and he becomes more and more violent and erratic as the battle with Deku and co. drags on. 

Animal-loving

As far as I know there is no canon evidence for this, but this adorable fanart by @ghostalebrije of Stain with a kitty friend gives me life. Maybe before his killing days Stain had a pet. Hell, maybe even as Stain he still had animal friends. He had to live somewhere in-between his hero-hunting, right?

Flexible

Physically, very. In battle we see that he gives it his all even in disadvantageous situations and combats multiple Quirks and battle styles, often at the same time. By analysing them as he fights, Stain proves himself a formidable opponent. 

Personally, not so much. He is so driven and committed to his beliefs that anything outside the confines of his own moral code and ideals is rejected. For instance, he rejects Iida’s commitment to changing his ways, insisting that Iida will “always be a fake”. 

This flaw in his methods/logic could be said to reveal a defensive mechanism that Stain employs to keep himself going. For example, if he were to admit that heroes he despises, like Iida, could change, then years of training and bloodshed and despair would have all been for nothing, in Stain’s eyes. If he admitted his methods were wrong, or that he could have gone about it all differently, Stain may not be able to psychologically deal with it.

This black-and-white view of heroism does not account for those who wish to attain hero status for selfish reasons, but those reasons involve benefiting the lives of others (e.g.: Ochako) and which will not interfere with their duty towards society.

Cheerful & Optimistic

In his younger days Stain was more like Deku, a starry-eyed kid dazzled and inspired by All-Might and dreaming of nothing else but following his example and helping others. If he had followed that path, Stain would have been happier for it.

The reality, unfortunately, is that Stain has become a bitter, rage-filled adult consumed by his ideology, hating the hypocrisy and vanity of pro heroes. He takes no joy in killing, though he perceives it as a necessary evil (he never smiles or laughs like maniac when killing or facing opponents). His conviction and killing intent were born from the despair and hopelessness he felt as his words and ideal view of a hero were ignored by society at large. He generally comes across as a very, very unhappy man who has all but killed himself for the sake of others. 

Once he was a cheerful youngster, full of promise, but no longer.

As for optimism... it depends. When it comes to individuals, Stain is pessimistic. His black-and-white morals guarantee that those heroes he sees as immoral/fake will always be so. 

On the other hand, Stain believes that an ideal world can be achieved, and that through heroes like Deku the corrupt hero system/community can be reformed, and that this will in turn benefit wider society. He does have confidence and hope in the future... but only he and people who share his ideals can act upon it. Stain’s optimism is, therefore, narrow.

Worst Traits

Irresponsible

If anything, Stain puts far more responsibility on his shoulders than any human being out to. While he may not be under the illusion that he alone can purge all the ‘fakes’ in hero society, he places himself as the one whose sole duty it is to make society see the ‘fakes’ the way he does and acknowledge his worldview.

He wants to be the giant red stain that makes society realise just how dirty it has become. It is a path to self-destruction that no human mind and body can take for long, and while his actions did have some short-term benefits (e.g.: lowering crime rates in the places he was active due to hero awareness) in the long-term they, however unintentionally, caused more misery and danger than before.

Forgetful

Stain literally forgets Deku’s recovery time as he becomes more and more stressed and pressed for time, costing him the battle. 

It’s difficult to attribute this trait to him with solid evidence otherwise. You could say that Stain has become so obsessed with his goals and motivations for killing that he has forgotten who he used to be (someone very similar to Deku) and has lost a sense of perspective that could have helped him see alternative ways of promoting his ideals (like Deku does).

Selfish

Nobody asked Stain to take action on their behalf. Stain mutilated himself and stained his hands with blood, robbed himself of the chance of ever becoming a hero like All-Might (of which he had dreamed), committed himself to saving people from the darkness of alleys by killing heroes he sees as neglecting or outright abandoning their duties to the people.

I would argue, however, that Stain’s actions are selfless in the way Ayn Rand understood the word.

Rand writes, "[A]ltruism permits no concept of a self-respecting, self-supporting man—a man who supports his own life by his own effort and neither sacrifices himself nor others…it permits no concept of benevolent co-existence among men…it permits no concept of justice".

Stain has sacrificed his own body, mind and life on the altar of his ideals for the sake of a better society. Through his actions towards this goal, he eviscerates any opportunity of ‘benevolent co-existence among men’ and sacrifices others on a regular basis for the greater good. 

This is directly opposed to Deku, who can in this way be seen as selfish. Both live by All-Might’s quote: “Meddling when you don’t need to is the essence of a hero”, but while Deku supports his life and that of others in order to achieve his dream of succeeding All-Might and helping people, Stain does it without any thought to himself or the individuals he deems sacrifices to his cause.

Stain never asks for alternative opinions and outright rejects any notion different from his (like Iida’s). In the Illegals spin-off, his final words after cutting off his nose show that he has entirely ceased to view or respect himself as an individual but instead as an ideology, calling himself “one without an existence who takes action” and a “colour which dyes the world”. 

He is neither self-respecting or self-supporting (achieving his end goal appears to be the only thing he lives for and his bloody methods are “proof of his significance” - meaning he literally has no reason to exist unless ‘fake’ heroes give him that reason).

Stain has murdered his own sense of self for others. Personally that’s the most destructive example of altruism I can imagine.

Lazy

See ‘Active’ Best Trait. This man is only ever inactive when he is asleep.

Impatient

Stain is so desperate to revive the values and ideals of heroism that have been lost on the majority of heroes he has encountered that he is willing to kill to force society to pay attention. He has committed his life to be the “guiding bloodstain that cannot be wiped away”. He perceives killing (”purging”) fake heroes as the fastest route towards his end goal, abandoning his former, peaceful method of public speaking.

Unreliable

This is a tricky one, as so far I don’t think we’ve seen a moment where Stain was actually relied upon for anything. At a stretch you could say Tomura was relying on him to accept his invitation into the League of Villains, which Stain rejected. 

Stain works alone, and neither society or any individual relied on him to push for change.

Deku has, however, come to understand the Hero Killer’s motivations and ideals, and has defended him from the force of wanton destruction and chaos that is Tomura. Deku knows that Stain abides by his strict moral code and strives towards his goals at detriment to himself (as seen when Stain saved Deku from the Noma). In this way, it could be argued that Deku in particular could rely upon Stain to adhere to this code and his ideals no matter what.

‘Going own way’

Stain’s passion has become so intense and obsessive that it has almost entirely lost his ability to think of any other way of being and acting, and at its worst is expressed through bloodlust and a killing intent Deku and his friends know too well.