There are marked group differences in rates of crime, illegitimacy, poverty, and professional achievement even after controlling for IQ

According to Jared Taylor:

A black with an IQ of 115, for example, is more likely than a white of the same IQ to be behind bars or have an illegitimate child. And a white is more likely to be in those predicaments than an Asian of the same intelligence. IQ explains a lot, but doesn’t explain everything.

Richard Lynn has found consistent racial differences in the distribution of psychopathic personality as measured by standard tests. For example, US scores on the Psychopathic Deviate Scale of the Minnesota Multiphasic Personality Inventory (MMPI) show a consistent pattern: blacks highest, American Indians next, whites at the mid-range, and Japanese and Chinese lowest.

Also, diversity increases sectarian violence:

Mixed societies like Lebanon, Sudan, and the former Yugoslavia have chronic tension; homogeneous ones like Iceland, Japan, and Korea do not.