I really need help. Am following (GameFAQs: Final Fantasy VII (PS) Speed Run FAQ/Walkthrough by GarlandG) SpeedRun by GarlandG... but not really doing a speed run (just want to complete the game doing only the main storyline and no side quests.

I am stuck on Material Keeper and can't seem to kill him. I've tried both Cloud & Cait's way of poisoning/bio the material keeper. I can get Material Keeper to glow green but he just won't die.

Is there any other easier way to defeat this guy?