This is the 14182nd most frequent German word.
grausam
Cruel.
Here, 'grausame' is used as an adjective to describe the decision as being 'cruel' or 'harsh'.
Die grausame Entscheidung der Regierung verursachte große Unzufriedenheit.
The cruel decision of the government caused great dissatisfaction.
In this usage, 'grausam' intensifies the adjective 'spannend' (exciting), suggesting an extreme level of excitement.
Dieser Film ist grausam spannend—man kann ihn nicht stoppen zu schauen.
This movie is cruelly exciting—you cannot stop watching it.
The word 'grausam' serves in its core usage emphasizing the severe or inhumane nature of the treatment.