Hehehe... I guess my upbringing caused me to learn to hate people in a really targeted manner. But maybe we don't even need unforgivable curses. Umbridge got a life sentence in Azkaban, and although the dementors were removed by Kingsley Shacklebolt, who became minister for Magic after Voldemort's downfall, I've know that a life long sentence is enough to drive anybody crazy. I know that in the Netherlands, were a life-long sentence means you really are in jail until the day you die (parole is very hard to get and requires a personal pardon from the king himself and is rarely given), I did hear some inmates serving a life-long imprisonment that they'd rather have been executed in stead. This means they already suffer.
Death is the easy way out of everything. In Death Umbridge cannot repent for what she had done. Alive facing severe punishment, she can... The world is not just divided in unforgivable curses and going completely off the hook.