It’s an adverb that can be used in a number of different ways:
1 It can mean particularly savage and violent;
2 It can mean in a direct and uncompromising way, where no attempt is made to disguise unpleasantness;
3 It can mean to an extremely unpleasant or harsh degree;
1 He was brutally attacked in the street;
2 It was a brutally candid review of her performance;
3 The thaw followed weeks of brutally cold weather;
The small inconviences of daily life that gradually beat a man down to the point he can't help to moan the word "brutality" in order to ease the pain of these constant annoyances