Devil May Cry 4

Proud Souls are a form of currency in the game and they can be earned by completing levels. The better your rank and the higher your difficulty when you beat them, the more proud souls you will earn.

Proud Souls can be used to buy new moves and skills in game. Doing so will reduce the number of Souls you have but the achievement is for Souls acquired so you can spend as many as you like without worrying about the achievement.