If everyone is performing well in your school-based assessment tasks/exams, and this performance is maintained and reflected in the HSC exam (this applies to both French Continuers and French Extension), then ranking last will have a very negligible effect (if any) on your HSC mark. Considering the instance where you rank last, and being mindful of the moderation process, the lowest Assessment Mark, which contributes 50% of your HSC mark (final mark) is adjusted to equal the lowest Examination Mark, which contributes the other 50% of your HSC mark. In such a case, performance in the HSC exam in both French Continuers and French Extension becomes highly important. Let's go through an example using French Continuers, where you rank last internally. If you also achieve the lowest Examination Mark, your HSC mark will then most likely be equal to the Examination Mark. The only concerning aspect is if you rank last internally, but achieve the highest/second-highest Examination Mark for example as this implies that your Assessment Mark will be adjusted to equal the lowest Examination Mark, which in this case will be achieved by someone other than yourself, giving you no control over your Assessment Mark and potentially affecting your HSC mark.
La meilleure solution, c'est de travailler tous ensemble pour obtenir les meilleures notes possibles. Ainsi, t'auras rien à craindre.
Bonne chance !