No question that this is an immensely powerful, and certainly very scary performance from Forest Whitaker as Amin. He has not only captured the menace and malice, but also the unavoidable charisma of the man. This film is to be highly recommended.
Yet does it provide any deeper insights into the psychology of tyrrany? Not really. In fact the interesting characterisation in this story ought to be that of the fictional composite Dr Nicholas Garrigan, whose mis-judgements are its dramatic engine.
You don't come across them as often as the do-gooders that are only really interested in the raw deprivation, but alienated, nascent sociopaths, mouths open basking for adventure in all its available forms, are hardly that unusual out in the developing world. I recognise the outline of the type in myself, but have come across it in far purer concentration in others.
The trouble is that aside from Dr Garrigan himself and Idi Amin, the other protagonists in the story are comparatively thin, leaving the young doctor with the screen-filling dictator as his primary interlocutor. He functions well enough as a suitable witness to the murderous Ugandan President's dialogue (actually mostly monologue), but he needs some more of his own to better manifest his inner turmoil and transformation. The moments where he floats in water flashing back to key scenes earlier in the film don't really cut it.