You need to get 50-hit and 100-hit combos, respectively, to get these. There is a very easy spot to get these, which requires you to play on Crusader difficulty. In Chapter 2, Mission 6 "The Five Wells of Zara," you will fight a boss that has multiple stages. In the first stage of the battle, you'll be in Curse Mode and have to defeat all of the unpurified souls in the area before you move onto the second stage. The big idea here is that the boss is impervious to damage in the first stage, so defeat all but one of the souls, then attack the boss. Since you're playing on Crusader difficulty, any combo you do will stun the boss, so you can keep on attacking until you reach the number of hits required.