I feel if there is no obtective moral truth or standard, how should we judge the action. While Existentialism say we create our own meaning and values. Nihilism say no inherent meaning or moral truth. Which is right?

Consequentialism is a framework that argues action depends on its results not necessarily its intention. SSo at this point! There is a problem. Even though the morality and intention is right, if it causes harmful consequnces, it is wrong. Therefore, the standard of justice and morality could not be stablized.