diaboliser

To portray someone or something as evil, monstrous, or dangerous — very common in political and media commentary, where diaboliser l'adversaire (demonizing one's opponent) describes a recognized rhetorical strategy, not just casual exaggeration.

• La presse a été accusée de diaboliser le mouvement. — The press was accused of demonizing the movement.
• Il ne faut pas diaboliser toute une génération à cause de quelques excès. — You shouldn't demonize an entire generation because of a few excesses.
• Ses adversaires cherchent à le diaboliser depuis le début de la campagne. — His opponents have been trying to demonize him since the start of the campaign.

Learners sometimes reach for diaboliser when they just mean 'to criticize' — diaboliser implies painting someone as monstrous or as an absolute enemy, a much stronger and more loaded claim than ordinary criticism.