Stain

Appearance
Appearance stain is an intimidating, muscular man who walks with a Black Robe, and has face without a nose, which he removed himself, and an extraordinarily long tongue, tainted with numerous small papillae. He has rather long, black hair, which he wears in a messy fashion when he does not wear a helmet, it would drape over his face if not for his headband and mask, and small red eyes with tiny irises. He sports a dark combat suit, plated with metal armor across his body to holster his weapons. all the way from just below his shoulders to his wrists is covered with metal armor. He also wears long black hand guards with spicy nails, and his knees are protected with metal pads, the armor completed by black boots made for silent movement. He always dons his signature black mask, as well as the tattered cloth he wears around his head as a helmet.

Personality
Stain is a cold, unforgiving, and merciless man with a sense of duty to cleanse society of false knights. He believes that those who become a knight for fame or money or other reasons that sway from serving your king/master are unworthy of being called the name and only All Might is a true hero. Due to his strong ideology, he took it upon himself to become the Knight Killer: Stain to stain his own hands with blood to purge fake knights and change the current society.

Stain does not wish to kill those who are not targets for his own cause. He dislikes needless bloodshed, thus explaining why he came to blows with Tomura Shigaraki. He is reluctant to attack Treywill before the knight-in-training provokes him. He even tells Treywill the true traits of a knight in contrast to those who desire to use their Quirks in selfish ways. Stain spares Izuku Midoriya because he shows the characteristics of a true hero. He believes heavily in creeds and convictions, stating that they are needed in order to accomplish anything and that without them people are weak and will eventually die.

In spite of his extremist views and beliefs, Stain does have genuine ideals about Honor which he stands by firmly. He does not hesitate to save people he deems worthy of being called Heroes, does not like killing without reason, and will even give advice to his enemies. He seems to acknowledge that what he is doing is morally wrong, but believes that in order for society to be put on the right path, someone must be what he is, indicating he sees himself as somewhat of a martyr.

Stain's conviction gives him an incredibly murderous aura and bloodlust that paralyzed several heroes in fear. It gives him enough confidence to willingly challenge several pro heroes at once, even after sustaining major injuries.

As Stendhal, he believed that any who "wielded power without conviction" were automatically sinners deserving of death, and used this belief to justify his actions as heroic instead of hypocritical. That said, he was perfectly willing to work alongside villains like Kuin Hachisuka as a means to an end. Stendhal also appeared to suffer from a split-personality disorder of some kind that caused him to view his vigilante and civilian identities as two separate entities (his mental change signified by whether or not he is wearing his mask at the time). However, his confrontation with Knuckleduster caused him to change his beliefs, and start thinking that those who are not "true knights" are the reason for society's problems.