Difficulty stacking?

[shinobigarth]

anyone know if the completion achievements stack?

[xENVxGAMERSKREW]

They should be unless its like F4:ROTSS,shrek3rd that you gotta replay to get the achievements

[QuasidodoJr]

They do stack, but some of the mission specific achievements are outrageously difficult to accomplish in Easy and Normal, so you can only guess how hard they'd be in Hard mode.