How unadvisable is it to flip the protagonist into a villain?

Question

Essentially, I have a protagonist who I set up as a 'main' good guy in one of my series. However, in my final series, I intend to make him turn to the dark side and oppose my other protagonists (from my other series).**My question:**Should I avoid turning my protagonist into an antagonist? Are there any foreseeable problems with this? Will this be a problem for readers? Any tips or tricks to handle this?Thanks!EDIT (in response to comments and answers):I should've mentioned this before, but it's clear in his series that the protagonist-turned-antagonist is very devious, and he has had hostile intentions previously towards the protagonists of the other series.

Answer 1

A good guy gone bad is actually something that could work but you would have to play it carefully or you will lose your audience. You would have to show the slow and painful downfall of this hero as they become more and more disillusioned, eventually ending with a twisted world view that makes them the bad guy. Let me be clear though and say that this character can not be written in such a way that the audience hates them, rather it's better for feeling of pity and sadness to come from watching someone fall from such noble heights. I will also say that this can not be a sudden change, it's not realistic for people to pull a 180 (or even a 90) out of nowhere.

Basically, yes, it can be done but you'll have to invest some time into learning how to do it well.

Answer 2

In storytelling, people typically don't like to feel fooled. Your audience wants to feel smart, and switching the role of the protagonist like this would make the entire experience of reading and investing in the story off-putting. As a possible work around, I'd recommend either making your narrator come across as unreliable, so that the story is told through an unreliable lens, which would make the twist a bit more literary, AND/OR I'd make sure that this switch is short-lived. The bad guy is twisted and ends up redeeming himself/herself in the end somehow. People want to walk away from a series liking the protagonist-- unlikeable protagonists tend to be hard to read, and it'd be very hard for a series to survive that.