Trump aka Dr. Strangelove:
President Trump has been described as being a pathological liar, a megalomaniac, narcissistic, delusional and suffering from attention deficit disorder. When one adds these symptoms up one has good reason to wonder if Trump is mentally ill or merely a sociopath. Of course being a sociopath itself may be the result of a mental disorder. Thinking he alone can take on North Korea OR like he claimed at the RNC that he alone could make "America Great Again" is a sign of delusional thinking.
A delusion is a belief that is held strong even when the evidence shows otherwise. Some common delusions associated with paranoid schizophrenia include, “believing that the government is monitoring every move you make, or that a co-worker is poisoning your lunch."
In all but rare cases, these beliefs are irrational, and can cause the person holding them to behave abnormally. Another frequent type of delusion is a delusion of grandeur, or the “fixed, false belief that one possesses superior qualities such as genius, fame, omnipotence, or wealth."