Hardly anyone would dare to call Dublin a criminal city. However, like everywhere else, if you don't adhere to basic safety rules, you can get into trouble.
For example, in the evening in the sleeping areas sometimes meet local gopniks. Fortunately, they do not pose any threat if you do not bully them and do not provoke a conflict. The citizens themselves consider the most dangerous areas of Dublin to be Baliemun, Finglas and Blanch. There are practically no hotels or inns here, so you are unlikely to risk unintentionally being in this part of the capital.