To answer your question, refer to these charts on the breakdown of US Army casualties in WW2 I made a week ago.

Source data comes from the Army Battle Casualties and Nonbattle Deaths in World War II Final Report, 7 December 1941 - 31 December 1946 report made by the US Army after WW2.

Regarding brutal, it's a matter of how you define brutality.

On the basis of KIA vs. non-fatal casualties, the European theater was less brutal with about 23.1% of casualties being fatal compared to 33.7% in the Pacific for the Army + Army Air Forces.

Indeed, on a rate basis, the average US ground unit was roughly 3x higher more likely to take casualties in the Pacific than in Europe.

However, as far as total casualties go, the European theater was more brutal by many folds. The top 10 locations for Army casualties shows that each location in Europe had many magnitudes more casualties than the Philippines, the largest Army operation of the Pacific, and total Europe casualties were over 750,000 for the Army alone, with 177,000 KIA, compared to ~170,000 in the Pacific (with 57,000 KIA)

By contrast, the Navy had about 34,000 KIA and Marines 17,000 KIA in the entire war. Source: Navy.mil - WW2 Casualties