If asked who is my favorite Abstract Expressionist painter, I'd probably usually answer Franz Kline (1910-1962). That's because he was bold rather than subtle, and I seem to retain a child-like preference for boldness over subtlety (I make exceptions, of course).
Poor Kline didn't quite make it to his 52nd birthday thanks to his bad heart. But from a strictly artistic-legacy point of view, his personal tragedy was possibly beneficial. That is, I'm not sure that he would have continued what he had been doing decades after Abstract Expressionism began running out of steam and fashion around the time of his death. What would he have done that would have been as aesthetically and commercially successful?
I'm not sure Kline's earlier painting would offer any clues, but I present some below as food for thought. They were grabbed off the Internet from here and there and I can't be absolutely certain that all of them were actually done by Kline. It's possible that there were misleading captions or misattributions, but this is hard to judge because Kline's early work is neither distinctive nor well-known.