The trailer for the final Avengers installment is here, and basically every Avenger is along for the ride. Iron Man, Spider-Man, Thor, Captain America, Chris Pratt, Dr. Strange, and seemingly all of Wakanda, whose king, T'challa (played by Chadwick Boseman), appeared to join forces with the team during the (spoiler alert) post-credits scene of Black Panther. Watch the whole thing above.
The villain in Avengers: Infinity War is definitely Thanos, a gigantic alien who wants to destroy "half the universe" for reasons that are not made clear in this trailer. Because Black Panther 2 is already in the works, he probably will not succeed. Find out for sure on April 27, when Avengers: Infinity War hits theaters.