The best way of getting these kills guaranteed is: Must be red bar enemies and I believe they can't be strikes either. Ogres: Starting up the Shrine of Oryx mission on Moon on the final cp WITHOUT THE HEROIC MODIFIER (LvL 9?) where your ghost first tells you that you are close and you can see the shrine. You kill the one RED BAR ogre and wipe by grenade or running back and jumping off the map. Hydras: Start "The Black Garden" mission on Mars and play until you reach the area where you must activate the hack doors to enter the final boss battle. This area is immediately after killing all of the harpies and dropping the barrier by killing the divisive mind. When you enter this area look on your right. There will be one hydra. Kill it and either grenade yourself or turn back the way you came and die to hobgoblins. These are the fastest and guaranteed ways of getting those kills, have fun!