There Are Actually Two Heroes That Ant-Man Has Never Met In The MCU
With a home base in San Francisco and a relatively recent entrance into the Marvel Cinematic Universe, Scott Lang, aka Ant-Man (Paul Rudd), hasn't had many chances to get involved with the Avengers and their many conflicts. If you recall, Scott's first team-up occurred in "Captain America: Civil War," and the consequences of that encounter led to his house arrest, as seen in "Ant-Man and the Wasp." Furthermore, after spending five years in the Quantum Realm, only to emerge into a post-Blip world and save the world with whoever is left, Scott can't be blamed for not being very social with Earth's Mightiest Heroes.
But, even with these brief interactions, there are still not that many MCU heroes that Scott has not interacted with thus far. He encountered a majority of these characters during "Avengers: Endgame," when his knowledge about physics and experience in the Quantum Realm inform the Avengers' plan to get the Infinity Stones back. He devises a theory that will allow the Avengers to time travel and bring back everyone lost in The Blip. This creates opportunities to meet many heroes, including during the final battle against Thanos (Josh Brolin) and, sadly, Tony Stark's (Robert Downey Jr.) funeral. But there are still two Marvel characters that he has yet to encounter.
Scott never hears Valkyrie insult his van
Although Scott Lang and Valkyrie (Tessa Thompson) never directly interact in the final battle in "Avengers: Endgame," they get pretty darn close. With the battle involving every known superhero fighting against Thanos' army, there's no question that it would be inconvenient to stop and ask for introductions. However, there is a moment in the final battle when Scott somewhat crosses paths with Valkyrie, and their teamwork helps the Avengers.
Scott proves to be the MVP in a moment of crisis when he realizes his van can be used to send the Infinity Stones back where they belong — if only it is in working condition. Valkyrie also has her hands full in the final battle as she rides her pegasus and battles Thanos' warriors. But she stops to answer Captain America's (Chris Evans) question if there is an ugly brown van anywhere. Technically, it is Cap who insults Scott's contraption, but Valkyrie doesn't disagree. It's possible Scott hears the response to the location of the van. He and Hope van Dyne (Evangeline Lilly) make it to the van to realize that it's dead, foiling another plan. However brief a remark, Valkyrie's comment doesn't count as a legitimate introduction, and the two are never seen in the same vicinity again.
Gamora isn't very social
Gamora (Zoe Saldana) is possibly the hardest hero in the Marvel Cinematic Universe to pin down. An assassin and adopted daughter of Thanos, she is usually in space or, as seen in "Avengers: Endgame," serving dutifully by her father's side. As such, there are a few key reasons Scott never has cause to meet her. Until "Avengers: Infinity War," Scott is on Earth while Gamora is out in space. Then, when Thanos uses her as a sacrifice to obtain the Soul Stone, well, that ends any opportunity of the two characters meeting.
But, because of different timelines in "Avengers: Endgame," this is not the last time the audience sees Gamora. An earlier version of Gamora — who ends up not being sacrificed for the Soul Stone — is part of the final battle. This would have been the only opportunity for Scott to meet her. However, she is too busy both saving and beating up Star-Lord (Chris Pratt) and joining forces with Nebula (Karen Gillan) to take much notice of the quippy Ant-Man.