Yes Lyon could easily double Fiorentina but even that favourable result leaves Liverpool needing effectively to get the better of Fiorentina over two legs starting the second leg 2-0 down. Even if they beat Fiorentina 3-0, Liverpool still have to get as good a result in Lyon as Fiorentina do at home to Debrecin.
If Fiorentina get a draw or win against Lyon, Liverpool could get through with a better than 2-1 win in Lyon if they also win their other two games and given how they struggled at Anfield against Debrecin, the Hungarians will be fancying themselves at home- they might well be challenging Liverpool for the Europa League slot if Liverpool don't buck up.
They are as good as out I tell you!