Size and strength doesn't mean it's going to win every single physical fight all the time.
Yeah, I agree. Being bigger doesn't automatically win fights. Another key factor to winning a fight is experience. For instance, in this one show that pitted animal against animal (all CGI, but with as much fact into it as possible), they had a lion and a tiger fight against each other, and the lion won not because of size (the tiger is bigger) but because of fighting experience. And in the wild, a female bear can drive away a male bear if her cubs are in danger, and she is, what, half the size of the male?
The reason I think Littlefoot stands no chance against Cera is because, well, just how much fighting experience has he had? Cera had siblings and thus likely roughhoused with them and learned some fighting skills that way, and that experience may have helped her beat Littlefoot (it also helped she was likely more headstrong than Littlefoot). Littlefoot, however, has no siblings and thus likely never had anyone to roughhouse with, thus never learned much fighting.
Even if Littlefoot was physically stronger than Cera, that wouldn't do him much good if he has little experience in fighting. Cera likely has a lot more experience in fighting and experience can outweigh strength at times.
Umm...no offense, but in that last ranking, I don't think you're giving Littlefoot's mother enough credit. If you recall, she single-handedly (tailededly? ) sent THE Sharptooth airborne to imprint his cranium on the surrounding geology no less than three times in the span of a few minutes, managing to do so on the third occasion even with a mortal wound on her back. Neither Bron nor Littlefoot's grandfather managed anything like that on any of the occasions we've seen them fighting sharpteeth.
Yeah, Littlefoot's mother was one heck of a fighter. From what I understand, females can be more tenacious than males, especially when it comes to defending their young. They can have more fighting experience on their side since they have to defend not only themselves, but the lives of their young. I would say that females can often be even more dangerous than the males, even if the males of that species is bigger.