Final answer:
The most severe potential consequence of nationalism is genocide, where the desire for a homogeneous national identity can lead to the systematic destruction of minority groups.
Step-by-step explanation:
One of the most serious potential negative consequences of nationalism is genocide. Nationalism can create a strong sense of identity and unity within a nation; however, it can also lead to the exclusion and dehumanization of those who are not part of the dominant national group. This exclusion can escalate into severe discrimination and, at its worst, can result in the systematic attempt to destroy or eliminate an entire group, recognized as genocide. Historical examples include the Holocaust during World War II and the Rwandan genocide in 1994. Nationalism's desire for a homogeneous national identity can sometimes lead to the persecution of minority groups, with catastrophic consequences. Therefore, it's imperative to remember the potential for nationalism to divide and to understand that it must be balanced with respect for diversity and human rights.