Avengers: Doomsday - Character Breakdown

In the build up to Avengers: Infinity War, Captain America: Civil War was used to drive a stake into the team that was Earth's Mightiest Heroes, leaving their alliance shattered. When Thanos came, Earth needed the Avengers more than ever, and they were broken.

Similarly here, in the build up to Doomsday, Thunderbolts* appears to be driving home the point that the Avengers aren't just broken or knocked down, they are gone. The MCU has gone one better and gotten rid of the Avengers completely this time, though Sam appears to be trying to build them back again in the background.

This is where Sentry (Lewis Pullman) comes into things, with Val apparently using the character as something of a replacement. He is billed in one of the Thunderbolts* trailers as being more powerful than all the Avengers combined, however he is then portrayed as the villain, with the titular team having to come together to stop him.

Of course, Sentry, a hero in the comics with powers comparable to Superman will wind up on the side of the good guys, similar to the arc of Will Poulter's Adam Warlock in Guardians of the Galaxy Vol 3, and will be a key part of the Thunderbolts*, New Avengers, or whatever the team ultimately calls themselves going forward.