Alexander Hamilton once called the national judiciary "the least dangerous branch." Was he correct?
I would tend to agree with this statement. I will talk about why the judiciary cannot be much of a danger (rather than talking about why the other branches can be dangerous).
First, the judiciary can only respond to cases that are brought to them. They cannot go out and proactively get involved in whatever area of policy they like. This greatly limits their scope as they cannot act on taxes, health care, foreign policy, things like that.
Second, the judiciary must rely on the other branches to carry out its judgements. If the judiciary's decisions are too far out of the mainstream, they are not likely to be enforced (for example, their decision in Worcester v. Georgia that Pres. Jackson would not enforce). This will seriously damage their credibility and they will want to avoid that.
So, even though judges are unelected and cannot really be removed, they are unable to do all that much compared to other branches. They cannot touch many areas of policy and even in the areas they can effect they must be careful not to be too radical.
I think that Hamilton is correct in his assertion. The primary function of the judicial is to interpret the Constitutionality of laws and actions of the legislative and executive branch. In this respect, its power is limited to being a strong response to the other two. It does not have the explicit powers of being able to initiate anything, and in this respect, it represents the least amount of danger because it is not going to do anything that will plunge the nation into peril. At its worst, it is going to interpret the Constitution, which cannot be considered dangerous because this is the essence of American jurisprudence and the "supreme law of the land."