Originally Posted by Nathan
Man, you really do defend anything. There wasn't anything special about Optimus, he was just good at kicking ass. We get the line that only a Prime is capable of defeating him, but they never bother to explain why. We are simply not supposed to question it. The Fallen had all the advantages and could have easily obliterate Prime before the fusion with Jetfire.
We're just supposed to take the storyline's convenient and lazy explanation.