I am not saying you are wrong, but I also fully understand yeongwoon's pov and I think i would do something similar if I were in his situation. He took a step to work on healing himself and he started taking medication, and the last step would be to forget. Taking revenge just wastes your time and energy and thinking about it everyday will make incapable to function properly. He HAD to make himself forget to keep pushing forward. But ultimately he didn't process or address the effects of what happened to him so he wasnt able to heal fully. He was baiscally putting a bandaid a gunshot wound (temporary solution, doesnt address the real issue). Taking revenge still won't heal him

Many might disagree with me but still wanted to express my opinion. I think that SeoIn made the right call, even though Yeongwo told him that they could just forget everything. I believe that is is easier to pretend that something bad didn't happen, maybe to protect yourself or just as a coping system. However its important to remember that Yeongwo suffers a lot, he has to take medicine for anxiety. If SeoIn manages to take revenge i think that they can truly close that bad chapter. I might me wrong, we will see later..