Something I have heard a million times before is that a character has to have an arc. That a character has to be different at the end of a book. Something that I fully believe in. But some people misunderstand this saying, and they interpret it as, “a character should be better at the end of a book, should have improved.” Now that I do not agree with.
An arc doesn’t always make a character better, sometimes life really screws you over and we don’t always learn from these experiences. Sometimes characters go from being the good guy, to a villain. This is also a character arc, it just isn’t a positive one.
And honestly, although I love redemption arcs, a well done villain arc I find to be even more fascinating. But, doing a villain arc means sacrificing a character to the dark side.
We don’t need to be that extreme to apply this same technique. Good example of character arcs that make a character worse (as in a worse person) could be, a character becoming less trusting, more paranoid, a character becoming faster to kill, less empathetic, a character losing their go happy nature. All of these are bad for the character but make for interesting arcs.
They should be reached in the same way as our usual characters arcs, often they are destined to be reversible (although this is in no way necessary). To avoid the trap of inconsequentiality, I always recommend that to reverse these arcs, either you take the same amount of time as it took to create them, or you sacrifice something to get there.
For example, if you’re previously good natured character has lost that happiness due to a traumatic event, and you want them to have it back, you could have them experience a very near death experience, maybe lose a limb, and somehow that reminds them how short life is and how there really is no time to mope.
On the other hand if you spend an entire book making a character more polite and respectful, then suddenly they head to an environment where that respect causes them to stick out and they want to forget it. They won’t do that overnight, make sure throughout the book it slowly reduces, until at the end of the book it’s no longer there.
There are many more possibilities for character arcs than character becoming braver or less impulsive. The best character arcs, just like the bests book, are not conventional.