My worst would include:
R-Point - a rare RoK take on the Vietnam War which just flounders in a supernatural setting.
Jarhead - I know it is beloved by most, but they've made a war film...boring.
Sand Castle - a wasted cast and some dreadful vehicle stand-ins. Not the worst...not the best. Gets better after the first 1/2 hour.
Pearl Harbour - Urrgh. Soapy, unrealistic, too long, too boring and too American. Dire.
Battle of the Bulge - great cast...greater errors.
Redacted - a good premise but they bottled the ending. Really bottled it.