An underrated but incredibly well-executed method of storytelling by Beyond Evil is their use of juxtapositions to compare and contrast the complexity and depth of its characters.
And the show best demonstrates this through the point of having two characters have similar circumstances or traits, but have them make entirely different choices.
One of the best juxtapositions are with two characters with the most in common with each other: Han Joowon and Park Jeongje. Both only children, both with a single parent who are both abusive and manipulative, both having risen in rank in their job through their family's connections, both connected to Lee Yuyeon's death—and most important of all, both of incredible importance to Lee Dongsik.
The difference was in their choices: Han Joowon acted immediately to rectify his mistakes and bring justice to Lee Dongsik—while Park Jeongje acted far, far too late.
Twenty-one years too late.
We also have two characters who are prone to outbursts of violence driven by high emotion—and this is an interesting juxtaposition—in Lee Dongsik and Kang Jinmook. The primary difference between them is that Lee Dongsik knows when to stop, to pull back before he can kill—regardless of how much he believes, because of his overwhelming anger and pain, that the other person deserves to die.
(Song Jiho very, very nearly did.)
Kang Jinmook doesn't have that restraint. Whoever he believes deserves to die, he thoughtlessly kills.
We have two ambitious figures of authority who don't think twice in getting rid of anyone who stands in the way in pursuit of their goal—to the point that they would both make use of their power to hide their own sons' sins—and yet at the end of it, it is only Do Haewon who finally broke down when Lee Dongsik quietly told her that her son, Park Jeongje, would kill himself if she didn't finally make the choice to do what was right.
In the end, between her ambition and her son, she still ultimately chose her son.
Han Kihwan instead chose to aim his own loaded gun at his own son's head.
We have a doomed marriage between Lee Changjin and Oh Jihwa, a toxic relationship built on lies and deceit by Lee Changjin; but we are given hope of what a healthy marriage and a loving nuclear family can be with Kang Dosoo and Im Seonnyeo.
We have two impassioned partners who aren't afraid to put themselves in danger in pursuit of justice—but only one of them listened to Lee Dongsik. Where Lee Sangyeob went ahead to thoughtlessly pursue Song Jiho, leaving his partner behind—Han Joowon chose to wait for his.
We have corrupt officials in the force like Jung Cheolmun, and yet where most police officers who would bend the rules for their own benefit—Lee Dongsik among them—we have a shining example of someone pursuing justice within the letter of the law with Oh Jihwa.
We mourn the loss of Lee Dongsik's other half, Lee Yuyeon, which is why we understand why Oh Jihwa could not bear to surrender Oh Jihoon to the authorities despite first finding out about his lies, because we know that just like Lee Dongsik, she would not bear the loss of her sibling.
We have two men both born into privilege, nepo babies who had everything served to them on a silver platter, and yet when forced to face a grave mistake, one chose to run from that mistake for twenty-one years, turning a blind eye to all the other deaths that occurred in its wake because he was too cowardly to face the consequences of his actions.
The other not only sought his own punishment for his own inadvertent abuse of power and negligence—he also brought down the most powerful cop in the country.
He brought down his own father.
One Han was the source of all the bloodshed—and the other Han ended it all.
There may be plenty more that I may have missed, but it's so fascinating how just by these examples alone, it powerfully demonstrates where evil truly lies, what will make you a monster—and ultimately, conversely, what will make you rise above all of it.
Because it's not the circumstances that will define you—but your choices.
It's not what happened to you—but what you choose to do.
It's not the life you were born into—but the life you choose to live.