It is quite rare for any pokemon not of the dark type to become seen as a symbol of evil, but the usage of Kadabra during the war have made them more than deserving of that title. In battle, of course, they were no more good or evil than any other pokemon, but their usage on prisoners of war is the sort of atrocity one would expect of Darkrai, not a psychic like Kadabra.
It is no accident that the torture squads of the regime whose name is forbidden to be spoken had two lightning-bolt 'S's on their uniforms. Officially, they stood for Soul Silver, the name of the paramilitary order, but they were quite clearly based on the markings which appear on every Kadabra's stomach. Most of these trainers carried Kadabra, and they would enthusiastically take part in the abuse of prisoners of war and captured dissidents.
After the war, most of those who were broken said that they could endure thumbscrews, the rack, and waterboarding, but not the agony of Kadabra's personalized psychic attacks.
