The main villain in the Marvel Cinematic Universe film Thunderbolts is The Void, the dark and evil alter ego of Robert Reynolds, also known as The Sentry

. Robert Reynolds/The Sentry is a complex character with a split personality: the heroic Sentry and the malevolent Void. The Void is an immensely powerful entity, described as stronger than all the Avengers combined, who can turn people into shadows and wreak havoc

. This duality makes The Void the central physical threat in the movie, while Valentina Allegra de Fontaine plays a manipulative role behind the scenes

. Originally, early drafts of the film considered John Walker/U.S. Agent as the villain, but the final version settled on The Void as the main antagonist

. In summary:

• Villain: The Void (evil alter ego of Robert Reynolds/The Sentry)
• Portrayed by: Lewis Pullman
• Powers: Superhuman strength, flight, energy projection, ability to turn people into shadows
• Role: Main physical threat and villain in Thunderbolts
• Additional antagonist: Valentina Allegra de Fontaine (manipulative figure behind the scenes)

This makes The Void the primary villain the Thunderbolts must confront in the film