Charles is the crown prince of France, and a smooth talker as well as an ambitious military leader. He's started a revolt against the English and is doing quite well when the play starts. He's understandably feeling pretty good about this, and he gives a great speech comparing the French to Mars, god of war. It's beautiful, Oscar-winning material.
The only problem is that Charles is soundly beaten by the English just a little bit later in the scene. So he thinks he's Sean Bean, a massive manly man, but he's maybe more like Orlando Bloom, kind of artsy and likely to be give flowery speeches. Though in fairness to Mr. Bloom, lots of his characters do their fair share of fighting, and in fairness to Charles, he has won a bunch of towns by this point.
Still, Charles could be more macho, especially if he's going to go around comparing himself to Mars. In the next scene, he says he'd rather die than retreat—but then he runs from the English, blaming his soldiers and saying he wouldn't have done it if his men weren't so cowardly. Because nothing's braver than running from battle and then blaming the crew you lead for your decision to do so…
When Joan shows up, Charles is smart enough to test out her knowledge, but after that he falls in love with her on the spot, gushes about how much he loves her, and pretty much lets her lead the armies. While in the 21st century we might applaud his decision to trust the best woman with the job, Shakespeare's audience likely would have been a bit suspicious of a king who falls in love at first sight and then thinks the woman he admires will lead an army better than he will.
Also, Charles is maybe a bit of a Renaissance British stereotype of the French, with really exaggerated courtly language and a tendency to not quite live up to it. It wouldn't surprise us if the original actor was faking a French accent like something out of Monty Python.
But Charles does have some actual chivalry, which we see when he protects Talbot's body. And let's not forget he's done a lot more fighting than Henry VI. So it's not like he's a complete joke—it's important to the clout of the English that he be a worthy opponent—but he's also not quite the man he claims to be.