Summary

• Bruce Banner's Hulk has undergone various iterations throughout the MCU, from uncontrollable to gladiator to Smart Hulk.
• The Hulk has been a crucial member of the MCU's superhero storylines, particularly after he became a founding member of the Avengers, when he brought back Thanos' snapped victims and through his training of Jennifer Walters' She-Hulk in Phase 4.
• The Hulk has appeared in alternate realities in the What If...? series, showcasing different versions and even new power upgrades.

Marvel Studios has shown Bruce Banner's violent transformation into the Smart Hulk in Avengers: Endgame.

Bruce Banner's MCU story began with an experimental attempt to recreate the super-soldier serum that transformed Steve Rogers into Captain America during World War II. Replacing vita rays with gamma radiation, Banner inadvertently altered his physiology, meaning that whenever his heart rate increases to 200bpm, he transforms from a regular human into a giant green monster. This process has been seen on many occasions over the duration of the MCU, both in the MCU's main live-action continuity and across the alternate realities of the multiverse.

19 Bruce Banner's Original Experiment Creates The Hulk

The Incredible Hulk (2008)

The opening montage of The Incredible Hulk detailed Bruce Banner's first transformation into the Hulk. Observed by his love interest and lab partner Betty Ross and her father, General Thaddeus Ross, Banner undergoes an experiment in an attempt to recreate Dr. Abraham Erskine's super-soldier serum, but with dire consequences for Banner. This transformation startles the Hulk, ending with him inadvertently injuring Betty and her father, and leading to a years-long man-hunt for Banner.

18 Emil Blonsky's First Attack Triggers The Hulk

The Incredible Hulk (2008)

While hiding from SHIELD and the United States military as a worker at a bottling factory in Rio de Janeiro, Bruce Banner seeks a cure for the Hulk. Unfortunately, his relatively peaceful life is interrupted by General Ross, who sends former special-ops commander Emil Blonsky to apprehend Banner and obtain the lost super-soldier serum experiment in his veins. Blonsky's first attack on Banner unleashes the Hulk, however, allowing him to easily defeat Blonsky and his team, but beginning Blonsky's transformation into the Abomination.

17 Emil Blonsky's Attack At Culver University Reveals The Hulk To The World

The Incredible Hulk (2008)

After being injected with another super-soldier serum, Emil Blonsky launches a second attack on Bruce Banner, following his return to the United States and reunion with Betty Ross. At Culver University, the military's attack causes Banner to transform into the Hulk, and the ensuing battle being caught on camera reveals the future Avenger to the world. Even though Blonsky has been enhanced with super-soldier serum, he is still easily defeated by the Hulk, who takes Betty Ross to safety, showing some semblance of humanity.

16 Bruce Banner Begins To Transform Into The Hulk In Samuel Sterns' Lab

The Incredible Hulk (2008)

Bruce Banner and Betty Ross' hunt for a cure for the Hulk leads them to Mr. Blue, a.k.a. Dr. Samuel Sterns. Banner and Sterns had been exchanging data for several months with the hope that the latter could cure the former's infliction. During the test of the cure in Sterns' Harlem laboratory, Banner begins to transform into the Hulk, but soon reverts to his human form, never completing the transformation and seemingly proving that the cure has worked - though this would soon be disproved.

15 Bruce Banner Jumps From General Ross' Helicopter

The Incredible Hulk (2008)

Following Bruce Banner seemingly being cured, Emil Blonsky blackmails Samuel Sterns into injecting him with Banner's gamma-irradiated blood. The Hulk's blood combines with the super-soldier serum already in Blonsky's body, transforming him into the grotesque Abomination. With the Abomination wreaking havoc throughout Harlem, Bruce Banner jumps from a military helicopter and transforms into the Hulk, allowing him to battle the Abomination one-on-one in a more evenly matched battle, which the former would eventually win, earning him freedom from SHIELD and the United States military.

14 Bruce Banner Controls His Hulk Transformation

The Incredible Hulk (2008)

Throughout The Incredible Hulk, Bruce Banner's transformations had been shown to be completely unpredictable and uncontrollable. However, the final moments of the 2008 film prove that Banner finally has a hold on his condition. Through meditation and breathing exercises, Banner begins the change on his own volition. This control would later be demonstrated brilliantly in 2012's The Avengers, though this would be the last time that Edward Norton is seen as Bruce Banner's Hulk in the MCU.

13 Loki Attacks SHIELD's Helicarrier

The Avengers (2012)

Mark Ruffalo's Bruce Banner becomes one of the six initial recruits for the original Avengers team in 2012, being brought onto SHIELD's helicarrier to track the stolen Tesseract. Unfortunately, Loki's mind-control of several SHIELD agents, including Clint Barton's Hawkeye, allows him to attack the helicarrier, which triggers Banner's transformation into the Hulk. This leads to a battle between the Hulk and several SHIELD agents and new superheroes, such as Natasha Romanoff's Black Widow and Thor, which ends with the Hulk being thrown from the helicarrier and falling to Earth.

12 Bruce Banner s The Battle Of New York

The Avengers (2012)

Despite being separated from the Avengers during the attack on the SHIELD helicarrier, Bruce Banner still s his fellow superheroes for the Battle of New York. There, he gets the opportunity to prove his control over the Hulk, as he quickly transforms into his stronger alter ego and immediately brings down a Leviathan with a single punch. The Hulk proves pivotal in defeating the God of Mischief Loki, as he batters the Asgardian villain in Stark Tower, dubs him a "puny god," and saves Tony Stark's Iron Man during his fall back through Loki's portal.

11 The Hulk Fights HYDRA With The Avengers

Avengers: Age Of Ultron (2015)

Bruce Banner was missing for most of the MCU's Phase 2, but he returns alongside the other Avengers in the opening moments of 2015's Avengers: Age of Ultron, fighting HYDRA forces at a Sokovia outpost led by Baron Strucker. Bruce Banner's transformation into the Hulk prior to Age of Ultron's opening wasn't seen on screen, but these moments did show his budding connection and romance with Natasha Romanoff's Black Widow. Romanoff is shown to be able to lull the Hulk back into Bruce Banner, calming him enough to bring some semblance of control to the strongest Avenger.

10 The Scarlet Witch Manipulates Bruce Banner

Avengers: Age Of Ultron (2015)

While Bruce Banner was shown to have some sort of control over the Hulk prior to Avengers: Age of Ultron, the introduction of Wanda Maximoff's Scarlet Witch unleashes the savage Hulk once again. The Scarlet Witch's manipulation of Banner sends the Hulk on a violent rampage through the streets of Johannesburg, where he enters into battle with Tony Stark in the Hulkbuster armor. This catastrophic event puts the Hulk back in the public eye as a destructive force, rather than a hero, which is ironically the same treatment Wanda Maximoff sees in the opening moments of Captain America: Civil War.