Over in the controversial opinions thread, there has been an interesting discussion that I think deserve a better showcase.
There is a very interesting analysis of Wonder Woman's movie fighting styles over on Yotube. Well worth a look, if you haven't seen it.
If we are to look at pankration images, it seems that the hand strikes are more boxing-style than karate-style, so taking some boxing techniques might make sense. On the other hand, the use of karate (or tae kwon do) style hand strikes doesn't really bother me, because the Amazons might have their own techniques that only partially overlap with historical pankration, and also since they might have developed it on their own for a very long time.
But you see lots of holds and chokes, so freestyle wrestling should be a natural style to be inspired by when designing how Diana fights. It is also close in and brutal.
In a way, I'd like Diana (and the rest of the Amazons) to more or less be able to at will switch between three combat styles, both when fighting armed and unarmed. One similar to capoeira or gatka, with lots of rotations, flashiness, and dance-like movements. One a grappling and wrestling style, drawing from pankration and its modern "descendants" like greco-roman and freestyle wrestling. Last one inspired by pankration, muay thai, or the Hawiian style that DrNewGod mentioned: direct, close-in, and brutal.
All three should be really usable and practical, but in different contexts. The "dance" should be used for multiple opponents, or when the focus is more on protecting yourself than hurting your opponent. The "grappling" to subdue a single opponent. And last the "direct" to kill or maim.