Tenko Shimura, also known by his villain name Tomura Shigaraki, is the primary antagonist of the My Hero Academia series and made his first appearance during the U.S.J. Arc. His evil actions and motives have caused terror and destruction throughout the world.
Shigaraki and the League of Villains has gone head-to-head with the hero society for a while now and just like the rest of the league members, Shigaraki made it his life's goal to kill All Might, the symbol of peace, and destroy the society he represents and to create a new society according to his values, but what caused Shigaraki to become so evil and heartless?
My Hero Academia: Is Shigaraki Beyond Redemption?
Unfortunate Beginnings
Born with the quirk - decay, Shigaraki was able to rot and destroy anything he touched, a deep factor that contributed to Shigaraki's evil actions was his abusive upbringing, his father constantly abused him for looking up to heroes, this further reinforced Shigaraki's feelings of rejection and unwantedness, causing him to wonder why the world hated him, and he began hating the world in return.
Due to his quirk, Shigaraki ended up accidentally killing his family members but purposely kills his father because of the abuse he received from him over the years for supporting heroes. The now orphaned Shigaraki roamed the streets expecting people to help him, but society just assumed that heroes would take care of him, upsetting the young boy even further. Shigaraki was seen as an outcast to society and was constantly rejected by those around him, and he always felt that he didn't belong to society because he didn't fit in with the world around him, he slowly began to resent society more, especially the heroes. After the death of his family, Shigaraki ran into All for One who took him under his wing and groomed him to become his successor.
The Descent To Evil
All For One saw the potential Shigaraki had and filled his head with hateful ideologies, causing him to become a vessel for All For One's desire for destruction and domination. The past and present experience with rejection and abuse of society fueled his hatred even more, and he gradually became consumed with anger. Under All For One's guidance, Shigaraki grew up with a negative view of the world, viewing all life as meaningless and valuing only his own desire for revenge. This was further reinforced by his experience as a villain, where he was constantly defeated by heroes and rejected by society. He also became the leader of the League of Villain, a group of like-minded villains who shared the desire to bring down hero society and society in general, and create a new world where villains could rule without interference from heroes.
Although Shigaraki is constantly seen as cruel and brutal villain, there is a sense of tragedy to his character, as he is mostly driven by the sense of loneliness and isolation. Unlike most people who are given the chance to make meaningful connections with their quirk, Shigaraki had to find out the hard way how destructive his quirk could be resulting in the loss of his family. He also later realizes that All For One was using him as a weapon and tool all this while never truly caring about Shigaraki's goals and desires.
Shigaraki's quirk "decay" is symbolism for the character's situation and his negative view on life. Shigaraki's journey from a traumatized childhood to a powerful villain was shaped by the factors of his quirk, relationship and his experience. While his actions are evil, they are also a result of deep pain and suffering he has endured throughout his life making him the powerful villain he is today.