I'm continuing the discussion of problem characters, and I think I've run out of them, so I'm open to questions or suggestions on either this topic or other writing topics you want me to address. The final (maybe) problem character is the Charismatic Villain.
This is another one of those "problems" that doesn't sound like a problem. A good villain can do a lot for a story. You want your villain to be interesting and memorable. It's only a problem when your villain doesn't quite fit with the story you're telling. If you've got a great villain with a sympathetic backstory that almost justifies his actions, lots of snappy dialogue, and all the good scenes while the heroes are either bland or fatally flawed, then it's not going to be very satisfying when the heroes defeat the villain. Or if you fall so in love with your villain that you can't bring yourself to defeat him and decide to redeem him instead, that's a problem if the redemption is out of proportion with his evil. You also have problems if readers are cheering for your villain to win and that's not the story you're telling (you'll probably always have at least a few villain apologists, but I'm talking about the general readership).
The problem is that villains are fun to write (and many actors say they prefer playing villains because they're more fun to play). You can let them say and do all those things you might think about but would never do. You can go all-out without worrying about whether they're still sympathetic. So what do you do if you've had a little too much fun writing your villain, and you find that your beta readers or critique partners like your villain more than your heroes -- and that's not what you want?
The first thing to do is do more work on your heroes. I addressed that earlier in talking about the good guy as a problem character. Heroes don't have to be boring (and I tend to think that writers who say that heroes are boring are lazy or untalented because that means they're either not trying or are doing it wrong). Heroes can have sad backstories and complex motivations. They can have funny lines and great scenes. Give your heroes the same care and development as you give your villains, and that will take your story to a new level. One classic example of this balance is the original Die Hard movie. The villain (aided by a brilliant performance by Alan Rickman) was so charismatic that in a way you found yourself sometimes cheering for him, but the hero (aided by Bruce Willis's snarky charm) also got great lines, got to be clever, and had a sympathetic story. Watching these two great characters go head to head was what made this movie so fun.
Or you could consider shifting the perspective. If you really love your villain and that's the best character in your story, maybe your villain should be an anti-hero protagonist, and either he gets to win and achieve his goals or he fails and is defeated by the good guys, and it's tragic. This is what you often see in gangster or crime spree stories, where the characters we're following would usually be the bad guys.
Or maybe if the villain is who you sympathize with the most, he could be a kind of bad boy hero and the star of the story, with some worse villain as the antagonist. You'd probably want to dial back the atrocities with this or with the anti-hero if you want audiences in general to sympathize with this character, but you can retain the troubled backstory and the snark.
Another option is the redemption arc -- let this character see the error of his ways and turn to helping the good guys against some worse villain. Then readers can be happy when team good guy wins because their favorite character is on that team. A well-done redemption arc can be a powerful story, but the redemption has to be earned and in proportion with the evil.
What it mostly comes down to is that you want your ending to be something that most of your readers will be happy with, and that means having the right characters be in the right place to have the right outcome that will be satisfying.