Thanos’ chilling presence in The Infinity Saga stole the spotlight of every other villain in theMCU. He is a genocidal Titan, who possesses powers like superhuman strength, intellect, durability, healing, and psychic abilities thanks to The Infinity Stones. The character was brought to life byJosh Brolin, who first appeared in 2014’sGuardians of the Galaxy, leaving viewers intrigued. Marvel strategically incorporated Thanos’ character and built anticipation in fans' minds for the biggest showdown of Phase 3. Initially, he remained a mysterious character who deployed his formidable army to pursue his ambitions. But his army crumbled when faced withearth’s mightiest heroes.
The Mad Titan’s mission was to bring balance to the universe by wiping out half of the population and halting resource depletion. He recognized that only the power of the Infinity Stones could help him achieve his goal. He forms various alliances that fail miserably in bringing him the stones. Driven by his twisted purpose, he decides to take matters into his own hands.Avengers: Infinity WarandAvengers: Endgamewitnessed the face-off between Thanos, his army, and the Avengers in the biggest battle of everyone’s life. While Marvel debuted the main antagonist a bit early, they had the opportunity to explore his character and relationships. But instead, they focused on his unwavering determination to complete his genocidal ambitions.

Thanos played minor roles with lasting impact in several MCU films before his grand entrance in The Infinity Saga. He made a debut in the post-credit scene ofThe Avengers, which revealed his involvement with Loki in the Chitauri invasion to acquire the Tesseract. Initially, the character was played by Damion Poitier, whom Brolin later replaced due to creative decisions.
Brolin’s portrayal of Thanos made a captivating appearance for the first time inGuardians of the Galaxy, offering a glimpse of his immense power and command to obtain what he wants. Faced with betrayal by his adoptive daughter, Gamora, he threatens Ronan the Accuser to retrieve the orb containing the power stone. Also,he sends Nebula, his second adopted daughter, with Ronan to aid in the mission. By the end of the film, Starlord gives the orb to Nova Corps to keep it safe in a high-security vault.

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Disappointed by his alliance’s continuous failures to bring him infinity stones, Thanos wields the infinity gauntlet and decides to fulfill his destiny independently in theAvengers: Age of Ultronpost-credit scenes. From pulling strings from afar to playing a pivotal role in the final Avengers blockbusters, Thanos' complex character became a symbol ofan ultimate threat.

Missed Opportunities for Thanos' Character Development
Undoubtedly, Thanos is the biggest villain in the MCU so far. However, many opportunities were missed to delve deeper into his character arc. Thanos witnessed the death of his home planet Titan due to overpopulation and wanted to prevent the universe from suffering the same fate. Amidst presenting this philosophy to the viewers, his origin, relationship with family, and the people of Titan remain unexplored.
Although flashback scenes offered a brief overview of how Thanos adopted Gamora and made her a skilled assassin like his other children, The backstory of Nebula and the formation of the Black Order were neglected throughout the narrative. Also, Thanos often delegated other villains to complete his goals initially instead of utilizing his team of supervillains, the Black Order, which is created to serve him.
Following his defeat against the Avengers,Eros, the brother of Thanos, was introduced inEternals' post-credit scene. The newly-revealed sibling relationship could have added layers to Thanos' narrative while exploring the themes of conflicting ideologies, complexities, and theirsecret connection with the Eternals.
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Unexplored Marvel Comics Storylines
The Infinity Gauntletcomic book storyline had the potential to introduce Adam Warlock’s character in action in Phase 3. He was teased inGuardians of the Galaxy Vol. 2, which could’ve led to him teaming up with other Avengers to stop Thanos. In the comics, Thanos embarks on a journey to massacre people to impress Death. Although he succeeds, an internal conflict with his daughter, Nebula, gives the heroes an opportunity to attack him. Adam Warlock wields the gauntlet to undo Thanos' wrongdoings and resurrect the fallen heroes. His presence in the final battle could’ve altered the aftermath, saving Tony Stark’s sacrifice in Endgame. An interesting face-off between the Avatars of Life (Adam Warlock) and Death (Thanos) would’ve been interesting to witness.
Introducing a love interest of a genocidal maniac in the MCU could have been another unique take. Beyond being a ruthless and relentless villain, Thanos is a lover who could go to lengths to prove his love for Death in the comics. Marvel films restricted his character to being motivated to restore balance in the universe, retire, and live peacefully on his farm. But in the comics, he engages in battles solely to seek his lover’s attention. Thanos could have become the embodiment of the phrase “The villain will sacrifice the world for you” only if Marvel had incorporated Death’s character in The Infinity Saga. It would have added complexity and emotional vulnerability to his character, showcasing the desperation he could go to demonstrate his love for her. A Thanos and Death love angle had the potential to make the whole story emotionally charged. However, the directors chose to focus on the consequences of his actions and the aftermath by ditching the romantic aspect.
The MCU didn’t put much emphasis on Thanos' origin, but it’s worth noting that he is an Eternal in the comics. Thanos and Eros are the sons of A’lars and Sui-San. Thanos has a disfigured and purple face due to Deviant Syndrome. Whereas Eros doesn’t have a deviant gene, thus, a human-like appearance. The Mad Titan stands out from the rest of the immortals for his love of power and destruction. Incorporating the Eternals' heritage aspect of Thanos' character from the comics could have contributed to his distinct identity.