Synonyms for Low-grade:

adj.

inferior (adjective)
shabby, mean, second-rate, common, substandard, mediocre, bad.
second-class (adjective)
second class.

n.

disgraceful, pitiful, dire, embarrassing. shabby, low quality, chronic, advanced, asymptomatic, communicable, autoimmune, mediocre, common, acute, mean, congenital, catching, clinical, better, benign, second class, second-rate, substandard. inferior (noun)
second-rate, poor, bad.
low-grade (noun)
inferior.

Other synonyms:

dire, low quality, second class, chronic, pitiful, embarrassing. second-rate, substandard. mediocre. shabby. common. Other relevant words:
poor, pitiful, better, congenital, shabby, clinical, dire, asymptomatic, acute, mean, advanced, communicable, second-rate, common, embarrassing, autoimmune, chronic, mediocre, benign, catching, substandard, low quality, bad, disgraceful.