More intelligence means bigger scope for action, and more ability to get desired outcomes. Whether more intelligence increases risk depends on the distribution of accidentally bad outcomes in the new scope (and how many old bad outcomes can be avoided), and whether people will do malign things. On average very few people seem to be malign, so the main issue is likely more the issue of new risks.

Looking at the great deliberate human-made disasters of the past suggests that they were often more of a systemic nature (societies allowing nasty people or social processes to run their course; e.g. democides and genocides) than due to individuals or groups successfully breaking rules (e.g. terrorism). This is actually a reason to support cognitive enhancement if it can produce more resilient societies less prone to systemic risks.