To ruin utterly in character or quality
He died a broken-hearted man, prophesying the inevitable ruin of a nation which he himself had done so much to demoralize.
If you don't get those taken care of first, the pain that those problems cause could demoralize you and cause you to fall out of the sport of jogging forever.
demoralize the enemy by tossing one of the remaining sacks over the wall.
demoralize the Iraqi troops?
demoralize IX: It would be demoralizing not to believe there is a moral order to the universe.