I am a Halo Enthusiest that loves to talk about the universe. Though I may not be the best multiplayer, I play for the fun and the unforgettable moments. If you play for a good time and for a little competition, then im your guy.
The Flood Is by far the most powerful of species. If you have ever heard of the Juggernaut Form, which was an enemy from Halo 2 i believe that got deleted at the last moment (Its still in the coding so you can fight it through unconventional means), then you could get a grasp as to why the Forerunners had their problems with the Flood. This is not the reason as to why they had problems with it of course, Im just pointing out how powerrful this form is. It is pretty much a Flood "Boss".