We in reality, all the phases of a project managements are important, because if failing to do one will cause domino effect on the other phases. If we have to choose one, I think it would be initiation phase, because that is what decides the overall project. The intiation phase is also the most tedious because it is the phase where “devils in the detail” are the most important. Besides this, think closing phase could be the easiest or the hardest depending on how you planned your other phases. If you made sure everything was clear from the beginning then, the closing phase would definitely be the easiest.