Question: I read somewhere that an intact plot should have two outcomes, if the protagonist fails in his goal, something bad will happen and if he succeeds, there must be also an unfavorable result. By these he has to chose, pursue or not. So thus it mean I should put two consequences in my story?
There is no such rule, although it is a possibility.
Dramatica theory talks about the Outcome (whether the story goal is achieved) and the Judgement (whether the main character resolves his/her inner conflict in a good way).
In some stories, the goal is achieved, but the main character ends up worse off as a result. For example, in Romeo & Juliet
, the goal of ending the feud between the families is achieved, but it costs Romeo his life (and Juliet hers). We call such stories comi-tragedies.
On the other hand, in a traditional comic or happy ending the goal is achieved and the main character ends up better off, happier, or at peace (e.g. most romantic comedies and Hollywood films).
There are also comedies in which the goal is achieved and the main character ends up with a good Judgement, but the impact character suffers a tragic fate (e.g. The Fault in Our Stars
). Unfortunately, I don't have a name for this type of ending, but there are plenty of examples.
Often the impact character with the tragic ending is the villain of the story, in which case readers don't have a lot of empathy for him/her, since the villain's death is seen as necessary to bring balance back to the world. For instance, no one mourns the death of Lord Voldemort or Emperor Palpatine.
Of course, it is also common to make villains somewhat sympathetic by helping the reader understand what makes them antisocial or showing aspects of their personality that are more positive. Hence, many people feel sad about the death of King Kong or Frankenstein.
Bottom line: you have lots of options to create the ending you want.