Andy Serkis' Ulysses Klaue was first introduced in Avengers: Age of Ultron. The fact that Serkis was even playing Klaue was only confirmed a few months before the movie came out. Because the character plays a big role in the Marvel Universe, specifically in relation to Black Panther's storyline, fans are expecting to hear a lot more from him.
Though Klaue had one short fight scene in Ultron, his role wasn't shown as a huge plot point. From his part, moviegoers unfamiliar with the comics would only be able to identify him as a bad guy. Just yesterday, however, a much fuller character backstory was brought to light.
A fan-created Facebook page posted an HD still from Avengers: Age of Ultron. It’s a picture of the file Tony Stark pulls out about Klaue when the team is trying to figure out Ultron’s next move. According to Andrew Gifford, who authored the post, the text on the file reads:
"Ulysses Klaue was an assassin hired to take down T'Chaka at the Bilderberg conference in the case that he refused to negotiate Wakanda's resources including Vibranium. But, Klaue was also there personally, as the Panther killed his great-grandfather in the 19th century while this one was trying to annex Wakanda. He was paid ten million dollars for the kill."
Take a look at the image (via Marvel Cinematic Universe):
Though the file says Klaue was paid, it's still unclear whether or not he succeeded in killing T'Chaka. According to a rumor earlier this month, T'Chakas's death is yet to come. The rumor reported that T’Chaka - father of T'Challa, who will be the Black Panther - will meet his demise in Civil War, though it offers little in terms of detail about the death, such as how or when it occurs. In the comics, T’Chaka is betrayed and murdered by Klaw (his comics name) for Wakanda’s resource of vibranium.
However, when talking about Black Panther's role in Civil War, Marvel Studios President Kevin Feige said, "I think he and his father are saying, ‘A bunch of vibranium just got out of here and wreaked a lot of havoc. Maybe we can’t stay behind these borders anymore..."
This quote implies that T'Chaka is still alive during Civil War's timeframe. Though we'll have to wait until Civil War's release to learn more. Klaue's role as an assassin and Black Panther antagonist is at least confirmed for now.
Captain America: Civil War opens in theaters May 6, 2016; Doctor Strange – November 4, 2016; Guardians of the Galaxy 2 – May 5, 2017; Spider-Man – July 28, 2017; Thor: Ragnarok – November 3, 2017; The Avengers: Infinity War Part 1 – May 4, 2018; Black Panther – July 6, 2018; Captain Marvel – November 2, 2018; The Avengers: Infinity War Part 2 – May 3, 2019; Inhumans – July 12, 2019.
Source: Marvel Cinematic Universe (via CinemaBlend)