Gerard is a simply psychopath of the highest order. He is an absolutely ruthless hunter who will murder any supernatural for any reason. He constantly proves to be cold-hearted, merciless, and shows little to no emotion. Gerard never discriminates between his victims whether they were innocent or not, human or otherwise, and has no care for any collateral damage.
Gerard has, not only a thirst for blood, but also for destruction and terror. He shows neither guilt nor remorse for the constant monstrosities he's commits. During a peace summit, he easily betrayed and murdered three of his fellow hunters then framed the alpha Deucalion for their deaths, scoffing at the latter's peace proposal between the hunter groups and the werewolf community just to perpetuate further bloodshed, demonstrating he has no regard for life. Gerard is stoic in his conviction that all supernaturals should be killed and has no limits about how to accomplish this even leaving a trail of bodies in his wake.
Your own people!"
"They wanted peace too. Look what you did to them." - Gerard framing Deucalion
Gerard is a firm believer in the survival of the fittest. He holds self-preservation above all else, will betray or sacrifice anyone, and admits without hesitation he will commit the unthinkable to ensure his own survival. He threatened the lives of his own son and granddaughter to this end. He also heartlessly endorsed that his daughter-in-law Victoria commit suicide simply to obey the hunter's honor code, highlighting his cruel and selfish nature. His planning to be bitten himself to cure his cancer at the same time shows his being a massive hypocrite.
"You monster. ... You'll kill her too??!!"
"When it comes to survival, I'd kill my own son!" - Jonathan Corvis and Gerard
Gerard is also a highly skilled manipulator. He is as calculating as he is treacherous, having a reputation for always having a plan. When almost succeeding in curing his cancer, he efficiently played all parties involved using cold, clever tactics; he exploited his family during their hunt against Derek Hale, held Melissa's life over Scott's head in exchange for Scott being his spy in Derek's pack and acquiring the kanima as its new master. He is also very adapt at having people see things from his viewpoint. His upbringing twisted his daughter, Kate into becoming the sadistic murderer she is, something he most likely intended for and took pride in. Likewise he was able to mold into becoming a cold-hearted hunter using well-placed emotional hooks to corrupt her and played on Tamora Monroe's paranoia, vindictiveness and xenophobia against the supernatural resulting in her leading his new army in Beacon Hills when in truth he is the one pulling the strings.
"I've known Gerard for a long time. He always has a plan." - Alan Deaton about Gerard
Gerard Argent is the patriarch of the Corvis Argent family, and a fearsome, bloodthirsty hunter.
Gerard had a brother named Alexander Argent who, according to Gerard himself, was Bitten by the Alpha werewolf Deucalion. Alexander committed suicide to follow the Hunter's Code.
Gerard raised his children to be hunters of the supernatural, to believe in the Hunters' crusade, serving his own bloodthirsty nature. His parenting and tutelage twisted and brainwashed Kate, her becoming the sociopath she is, though Jonathan always had a sense of morals.
When Chris was younger, one of Chris' dogs contracted rabies. Gerard shot the dog to put it out of it's misery. He iterated to his son a merciless fallacy: "Anything that dangerous, that out of control, is better off dead". When Chris was 18 years of age, Gerard had him conduct his first gun deal, a simple exchange. Gerard purposefully left out the fact the buyers were Yakuza, Japanese mafiya. He wanted to see if Chris could adapt in the heat of the situation, testing his ability to survive.
A decade or so before the series time, Gerard headed a hunt for a werewolf that had killed two of their own people. This werewolf was eventually hunted, killed and cut in half.
Some time later a message came to the Corvis/ Argents through Alan Deaton who was emissary to the Hale family, a prominent Pack, that the Alpha Deucalion had proposed a peace offering, to bring an end to needless violence killing between the nearby Packs and the Hunters. Three hunters who also wished for peace accompanied Gerard to meet the Pack on equal grounds in an abandoned distillery.
The meeting commenced. Unfortunately Gerard had planned in advance for everything to go wrong. Incapacitating both parties with knockout gas after immunizing himself, Gerard then unveiled a spiked mace he'd stored in the distillery. Using the weapon to disguise it as a murder committed by a werewolf, Gerard struck down his fellow hunters right afterward, to Deucalion's horror. Gerard mockingly replied that his comrades wanted peace too, then blamed the alpha for their deaths. The psychopathic hunter then moved on to kill Deucalion's three Betas, the came upon the weakened alpha. Making fun of Deucalion's peace proposal and taking out two flashbang arrows, Gerard gouged out Deucalion's eyes, leaving the werewolf screaming in agony.
Gerard's actions resulted in Deucalion being framed for the faux peace summit and the dark path the alpha eventually went down, instigating the werewolf-hunter war that persisted to the present.
Prior to Season 2, Gerard learned he was dying of cancer. He became dependent on a medication stored in a private container. He decided the way to save himself was to receive the Bite to cure his illness. Learning of Kate's death in Beacon Hills, California and Derek Hale becoming an Alpha, Gerard made his way to the town.