leech vs bloodsucker

leech and bloodsucker both are nouns.

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

As nouns, leech and bloodsucker are synonyms defined as:

leech and bloodsucker: carnivorous or bloodsucking aquatic or terrestrial worms typically having a sucker at each end

Other synonyms of leech include hirudinean.

leech (noun)	bloodsucker (noun)
carnivorous or bloodsucking aquatic or terrestrial worms typically having a sucker at each end	carnivorous or bloodsucking aquatic or terrestrial worms typically having a sucker at each end
a follower who hangs around a host (without benefit to the host) in hope of gain or advantage

leech (verb)	bloodsucker (verb)
draw blood