medicinal leech vs bloodsucker

medicinal leech and bloodsucker both are nouns.

Word	Noun	Adjective	Verb	Adverb
medicinal leech	Yes	No	No	No
bloodsucker	Yes	No	No	No

As nouns, bloodsucker is a hypernym of medicinal leech; that is, bloodsucker is a word with a broader meaning than medicinal leech:

medicinal leech: large European freshwater leech formerly used for bloodletting
bloodsucker: carnivorous or bloodsucking aquatic or terrestrial worms typically having a sucker at each end

Other hypernyms of medicinal leech include hirudinean, leech.

medicinal leech (noun)	bloodsucker (noun)
large European freshwater leech formerly used for bloodletting	carnivorous or bloodsucking aquatic or terrestrial worms typically having a sucker at each end