Question

Why do you have to replace plus bon ina sentence with meilleur, but not when you're using moins bon?

Answer 1

You had best post that sentence! "plus bon" is like saying "gooder" and I'm sure you don't want that. It looks like you are using the following comparisons, superlatives:

good = better = best
bon(bonne) = meilleur(e) = le/la meilleur(e)

and of course, don't forget the plural forms

However you could say "less good" = moins bon(bonne) BUT in that case I would say:

bad = worse = the worst
mauvais(e) = pire = le/la pire

When in doubt about something, please post it in its entirety. Taken out of context, we may not provide the best answer!

Sra (aka Mme)

Answer 2

like you can't say "Le restaurant le plus bon est...",but you can say "Le restaurant le moins bon est...".