OK! Since The Avengers will be facing off against Ultron next week and against Thanos in 2018 (and 2019) Let's look beyond that to the uncharted territory of Phase 4. Assuming there is still an Avengers' Team (Hopefully Thanos doesn't win and kill everyone) What Villains would you like to see The Avengers face off against? Here is a list of my favorite Villains who I think should make an appearance in the MCU...
Kang The Conqueror.
He's the Ruler of the 30th Century and he plans to invade the Earth of the 21st Century with his time-traveling Fleet! Why? to save his present timeline mostly. Something happens in our time to threaten his existence so he does what any Time Traveling Emperor would do...He comes to Conquer us!
Iron Man needs to be a part of this story, or at least Tony Stark because Kang's Technology is all based on Stark Tech. Vision also needs to be a big part of bringing down Kang. While Robert Downey Jr may not be a part of the franchise at this point (we're talking post 2020) Vision will have to represent for Stark's Technical know how.
The Secret Invasion (Skrulls)
The Secret Invasion would be a great story-line to cover because they will have laid the ground work for it with the inclusion of Ms Marvel (Captain Marvel) The Guardians of the Galaxy and Thanos. In the Secret Invasion the Avengers have gone missing and have all been replaced by Skrulls posing as each Avenger.
While Iron Man probably won't be around for this story, and I'm not really sure who would be an Avenger post-Infinity War, Whoever is on this team would have to deal with their Doppelgangers who happen to be The Skrulls!
The Masters of Evil.
The Masters of Evil are another great choice because most of the Villains on that team will have been introduced prior to Infinity War. The easy choices are of course Baron Zemo, who will appear in Captain America: Civil War and also Doctor Strange's movie. Abomination, who appeared in 2008's The Incredible Hulk. Enchantress and Absorbing Man both have appeared (sort of) on Agents of S.H.I.E.L.D. Crimson Dynamo, was bastardized in Iron Man 2 and combined with Whiplash. Wonder Man, would be an interesting addition and a good way to introduce him before he eventually became and Avenger. Black Knight could also be a member of the Masters of Evil. He's another one of those characters that starts out as the Villain and later becomes an Avenger.
Avengers vs X-Men!
This one is probably a pipe dream and would take Fox Studios and Marvel Studios to sit down and hash out property rights, but could you imagine a live action Avengers vs X-Men? The sad part would be that neither RDJ or Hugh Jackman would be around to participate since Hugh Jackman is probably retiring from the role of Wolverine after 2018. We'd also most likely have Bucky as Captain America by this point as Chris Evans will be done playing Cap by 2019. On the plus side though we could have Spider-Man on the Avengers team right? It's really quite frustrating that both Magneto and Doctor Doom are property of Fox Studios. Doctor Doom really has NOT been done right yet by anybody over at Fox Studios but I do like Michael Fassbender as the young Magneto and Sir Ian as older Magneto. Stranger things have happened though, so why not Avengers vs X-Men?
So there you have it! My choices for possible Villains the Avengers would face in a post-Thanos MCU.