Adrian Toomes' turn to crime occurred late in life, but his mindset that only the strong survive was there when he was young. Adrian's older brother, Marcus, tried to raise Adrian but he was soon paralyzed from the neck down after a motorcycle accident. At the beach one day, Marcus begged Adrian to push him into the ocean, as he couldn't stand being paralyzed. He said that being in a wheelchair was unnatural and that he should be dead. Human beings were animals, just like any other. Adrian refused to kill his brother and Marcus derided him for being weak. (Friendly Neighborhood Spider-Man #15)
The fate of Marcus is unknown but Adrian went on to become an electrical engineer. He formed B+T Electronics with Gregory Bestman and there invented his flying harness. In his excitement, he ran to Gregory's office and there found documents that proved that Bestman had been cheating Adrian out of his share of the profits. There was also paperwork that allowed Bestman to take control of the company. Toomes retreated to his Staten Island farm to complete the harness. He later returned to B+T and took the money that he felt he was owed. (Amazing Spider-Man #241)
The thrill and ease of the robbery convinced him to pursue a life of crime. In the same day he stole a man briefcase "worth a fortune in bonds" and pulled off the heist of over a million dollars worth of gems that were being transported across town. As added bravado, Toomes left messages at a radio network, the police chief's office and the Daily Bugle's office, warning which items he would be stealing. Spider-Man was soon on his trail, to which Toomes thought "So Spider-Man himself is on my trail! Good! It will be amusing to finally face a foe worthy of my mettle!" Naturally, Toomes was eventually caught and sent to prison. (Amazing Spider-Man #2)
After three run ins with Spider-Man, Toomes was totally obsessed with killing him. He was so adamant about his death being at the hands of a Vulture, Toomes told a fellow inmate where he could find a spare harness outside of prison. (Adrian believed he was dying at the time.) He told Drago, the second Vulture, "I must tell you--for only he, who wears the Vulture's wings--will possess the power--to destroy Spider-Man! And Spider-Man must be destroyed!" (Amazing Spider-Man #48)
Revenge was always part of Toomes M.O. He got his chance after he was diagnosed with cancer, due to the energy that the harness produced. Fearing that he would die before all accounts were settled, Adrian finally found Bestman and killed him. He also evened the scores with many other criminals that had wronged him or tried to turn him in to the police over the years. (Spectacular Spider-Man #186) Toomes even tried to commit mass murder by infecting birds with a virus and releasing them into New York, killing everyone the birds came into contact with. He rationalized that if everyone that knew Adrian Toomes were to die, than he would die too, in a philosophical way. (He had been de-aged and wanted to be remembered that way.) (Amazing Spider-Man #396) He also took part in various schemes to kill Otto Octavius, after Otto had betrayed the Sinister Six.
After he beat the cancer, Toomes returned to crime. When he managed to land $20 million with Electro, Toomes planned to use his share to help his grandson, who had leukemia. (Marvel Knights Spider-Man #3)
Adrian Toomes: A Social Darwinist?
Adrian has always held people that he saw as weak in contempt. Perhaps he did take to heart his brother's opinion that people are animals. He mocked Bestman for passing out after Vulture kidnapped him (Amazing Spider-Man #241) and derided Spider-Man in his prison cell. "(Spider-Man) lacks the strength to use his powers for their greatest potential...To help a world that despises him? Seek approval from those that hate him? Its masochistic. Its pointless. Weak." (Friendly Neighborhood Spider-Man #14)
Social Darwinism isn't a psychological term but it does shed light on Toomes' world view. In sociology, social Darwinism believes that human evolution can be influenced by putting laws or social conditions into effect that will weed out undesirable people from society. Toomes' fixation on strength of mind and disdain for compassion does show a sort of elitist mindset. He doesn't care for others, unless they are related to him by blood, i.e. his nephew and grandson. (His nephew, Malachi was murdered by a gangster, "Black Alfred." After Alfred found out he had been used by the Vulture and Malachi, he killed the younger Toomes. Adrian was so enraged by his nephew's death that he he viciously beat the man until Spider-Man and the police arrived.) (Peter Parker, The Spectacular Spider-Man #45)
Psychopathology: Insecurity and Depression
So let's recap. Toomes' company was stolen from him, leaving him out in the cold. He'd worked all his life and now had nothing. For a man that hates weakness, this must have been a serious blow to his ego. An old man, he didn't have time to start over. Erick Erickson, a researcher into psychology of age groups, described the psychological challenges that a person faces in each stage of life. The final stage, sometimes called the "ego integrity/despair" stage, asks whether the person will look back at their lives with pride in their accomplishments or with despair. I think that Toomes was initially very proud of his flying harness invention but then despaired that he'd lost his life's work to Bestman.
Toomes's has been obsessed with is own death for years, even attempting suicide after his cancer diagnosis. While in battle with Spider-Man, Toomes screams at him "I refuse to go out like some pathetic old fool! Like those drooling, bed wetting mannequins in the nursing home! I'm going to go out the way I lived! Angry! Fighting! Clawing at all the traitors and liars around me!" After the harness bursts into flames and Spidey saves his life, the old man whimpers "Why didn't you let me die?" (Spectacular Spider-Man #188)
A Genetic Link?
Toomes claimed that he got a thrill out of the ease in which he stole the money from Gregory Bestman. So much so, he turned to crime for years to come. His brother was also a motorcycle rider. The nature of the accident that paralyzed him is unknown, but he did seem to be a thrill seeker. Ditto for Malachi Toomes, who got involved with the mafia. Some psychiatrists claim that psychopathology results from genetics, environmental and psychological factors.
Adrian Toomes is a man obsessed with his own image. Whether de-aged and demanding to be remembered as young and healthy or dying like a man and not a mannequin, his image is all important. At this late stage of his life, he may not have much time. Strength is what is important to him, as is the death of anyone who crossed him or his family. This self importance is a symptom of narcissism and it makes him very dangerous.