The tragic passing of Heath Ledger might be even more resonant due to 2008 possibly being his breakout year as a movie star. The 28-year-old actor had spent his career constantly fighting skepticism — first struggling to be considered a serious actor and then a bankable one. He seemed to be on the brink of finding that success with this summer's expected Batman blockbuster, "The Dark Knight."

Back in 1999, Heath had his first starring role in Hollywood with the teen romantic comedy "10 Things I Hate About You." Casting director Marcia Ross recently recalled to MTV News the younger Heath coming in to read for the part of bad boy Patrick Verona: "He had just arrived in L.A. and came in to read for us, like any actor. He just had this great quality, and was gorgeous and funny. Very charming. He hadn't been there so long — I think it might have been one of his first film auditions. He tested with Julia Stiles, and they had great chemistry."

"10 Things" might have given Ledger his first starring role, but the Shakespearean adaptation set at a high school was considered fluffier fare. " '10 Things,' he didn't want it to be lightweight," Ross remembered. "He did not treat it lightly."

So while "10 Things" was a success at the box office, Ledger was immediately pegged as a teen heartthrob — a title he wholeheartedly resisted. "After '10 Things,' he was waiting for something that would show him as a serious actor. He had offers but held out for that." And for the most part, he did hold out, working on varied fare such as "The Patriot" and "Monster's Ball," with mixed results.

But the real breakthrough for Ledger seems to have been when he was unexpectedly cast as Ennis Del Mar in Ang Lee's 2005 epic, "Brokeback Mountain." It's an award-winning performance that stunned both fans and critics and went on to garner Ledger an Oscar nomination. Avy Kaufman, casting director for the film, explained that she cast Ledger "because he was a wonderful, wonderful actor. Knowing his work and meeting him, he represented everything Ang had written." She went on to say that his "tremendous talent" ensured he was right for the role.

Ang Lee seems to agree. In a statement to People.com, the director said, "Working with Heath was one of the purest joys of my life. He brought to the role of Ennis more than any of us could have imagined — a thirst for life, for love and for truth, and a vulnerability that made everyone who knew him love him. His death is heartbreaking."

So Ledger had finally become an esteemed actor in the eyes of critics. But he hadn't scored much box-office success in years. Then, in August 2006, Warner Bros. confirmed the huge news that it had found its new face for the Joker in Ledger. An iconic role last embodied by Jack Nicholson in Tim Burton's 1989 flick, "Batman," many were distrustful of any new actor moving in on such sacred ground, and the announcement prompted doubt as to whether Heath could make the role his own. Near the end of 2007, co-star Christian Bale and director Christopher Nolan told MTV News that fans needn't worry.

"I think what Heath is doing is very adventurous," Nolan said. "What he's doing is very radical. It's very much what I wanted. I knew I needed someone really fearless." And when the trailer premiered in December, every type of fan imaginable was thrilled with glimpses of his deranged, grungy Joker.

Filming had wrapped on "The Dark Knight," and it seems the movie will be saddled with quite a few challenges leading up to its anticipated release on July 18. Ledger had recently been in London shooting another movie, Terry Gilliam's "The Imaginarium of Dr. Parnassus," although there's no word yet on how that film will be affected by the tragedy.

So 2008 might wind up becoming Ledger's most rewarding year on the silver screen yet. As Ross noted, "He wanted to have a wide range of roles and not repeat himself — and he accomplished that as an actor. It's very sad. He had a big future ahead of him."

(Watch Heath Ledger talk about his evolution as an actor in a 2005 interview with MTV News, and read his colleagues' and admirers' reactions about the tragic news right here.)