Walter Simmons

Walter Simmons is the main antagonist of the 2021 film Godzilla vs. Kong.

Personality
On the surface, Walter presents himself as an affable, well-spoken and calm man with a charismatic flare of bravado, who seeks to better mankind and help the world become a safer place - to that extent, he's expressly distrustful of Godzilla, seeing him as a threat to mankind rather than its savior. He justifies his machinations by saying that humanity retaking their former place as the sole dominant species is the only way mankind will survive and that the mere existence of any other apex predator is unacceptable in that respect, a delusion which scarcely veils Simmons' true colors. In actuality, Simmons' charisma and mask of nobility veils an obscenely reckless, arrogant and egotistical man whose only true motivation is to feed his own overinflated ego by surpassing Godzilla as the reigning King of the Monsters with his own artificial Titan, something he'd been intending to do ever since the events in San Francisco in 2014. No cost is too high for Simmons in the pursuit of his goals, as he callously engineers the deaths of thousands, even millions of innocent civilians to turn the world against Godzilla.

Simmons is incredibly smug, and he's overconfident in his plan and his less-than-competent daughter. He never perceives the possibility that his plans or choices might go wrong no matter how extreme or ludicrous the methods, nor the potential for unforeseen ramifications; and he's horrifically blinded by hubris and stupidity to the point it never occurs to him that utilizing Ghidorah's alien and partly-alive telepathic neurology for his creation might backfire on him and his agenda spectacularly. He also displays inherent immaturity and lack of impulse control to manchild levels - when the energy formula needed to lastingly power Mechagodzilla is obtained, he's immediately excited to upload it to the Mecha and frustrated by Ren's protests, and he overall becomes giddy with excitement whenever his artificial Titan is about to be activated. Simmons displays an inability to take criticism in that respect, seen in his reaction to Ren's aforementioned warnings (though to be fair, Godzilla was heading to the facility, so Walter may have also acted out of desperation as he recognized Godzilla's intention of destroying the facility with them still inside, leaving him no choice but to urge Ren to activate Mechagodzilla). His inability to take criticism is also seen in his express disdain for environmentalists purely because they interfere with his company's activities.

It's clear that Simmons overall is an extremely childish and self-absorbed man with a high opinion of himself, who is in possession of far too much corporate power for his or anyone else's good.

Maia Simmons
Although Maia and Walter are never seen interacting directly, Maia seems to trust her father completely and is wholly on-board with his philosophy. For his part, Walter relies on Maia in turn, entrusting her with the mission to take point on Apex Cybernetics operations involving Hollow Earth and seeing to it that the energy source found there is secured for Apex's use, and he expresses high hopes that she will succeed. According to the novelization, Walter tends to set up mind-games for Maia on her assignments, such as keeping her in the dark about Kong's involvement on her mission, to test if she's worthy to inherit his corporate empire.

Ren Serizawa
Walter relies on Ren as Apex's chief technology officer to make Mechagodzilla work using Ghidorah's remains, and the two work closely together and are often seen together. In many ways the two seem to have a strange working with relationship with Walter viewing himself as an eccentric father figure to the more cautious and uneasy Ren. Despite his clear fondness and trust in Serizawa, Ren quietly displays a sense of weariness towards his employer's plans. All of that being said, when Ren protests to an overenthusiastic Simmons rushing the use of the Hollow Earth energy formula in Mechagodzilla without testing, Simmons reacts like an eager child annoyed at an elder for interrupting them, quickly losing his patience and desperately telling Ren to "get in the goddamn chair [referring to the Mechagodzilla-piloting cockpit]".

Godzilla
Simmons considers Godzilla a threat to humanity, insisting that the existence of any Alpha Titan is a threat to humanity by its mere existence. Ever since Godzilla's existence first became known to the world in 2014, Simmons has dreamed of surpassing Godzilla by building his own artificial Titan and using it to challenge and kill him.

Godzilla vs. Kong
Since Godzilla revealed himself to the world in 2014, Walter Simmons has been formulating a plan to eliminate the Titan.

In 2022, Walter Simmons meets with eco-terrorist Alan Jonah in Pensacola, Florida, and negotiates the purchase of Ghidorah's surviving skull from him in order to use it as part of the control mechanism for an anti-Godzilla weapon. Although they successfully managed to build it, they were unable to fully power it. Later following Godzilla's attack on the Apex Cybernetics facility in Pensacola in 2024, Walter Simmons and Ren Serizawa seek out the help of geologist Nathan Lind in obtaining an energy source in the Hollow Earth to fuel their weapon and motivated him by showing off their company's Hollow Earth Aerial Vehicle, which should be capable of reaching the subterranean world. Walter also sends his daughter Maia Simmons to represent Apex for the expedition.

While his daughter Maia is off traveling with the expedition, Walter arrives in Apex headquarters in Hong Kong to oversee his creation Mechagodzilla's test run against an adult Skullcrawler. The test was a success with the mecha effortlessly tearing apart the beast, but at the same time the test once again demonstrated that without the energy from the Hollow Earth as an infinite power supply, the mecha would be unable to achieve its full potential. When Godzilla subsequently arrives in Hong Kong and fires his atomic breath at the ground, Walter is ecstatic since he correctly deduces that it means Maia has discovered and activated the energy source they need for Mechagodzilla. Walter upon receiving the analysis of the power source from his daughter then insists on using it immediately, despite Ren's hesitance.

Shortly afterwards Walter meets Madison Russell, Josh Valentine, and Bernie Hayes when security guards catch them sneaking into the facility. Walter then proceeds to explain to them the purpose of Mechagodzilla and how he intends to exterminate all Titans so that humans can remain the dominant species. As Mechagodzilla is being fueled with the Hollow Earth energy, Walter continues to gloat about his success and thus fails to notice that the new energy source has allowed his creation to be hijacked by the remnants of Ghidorah's consciousness until it is too late and he is killed by his creation.