slugger vs ballplayer

slugger and ballplayer both are nouns.

Word	Noun	Adjective	Verb	Adverb
slugger	Yes	No	No	No
ballplayer	Yes	No	No	No

As nouns, ballplayer is a hypernym of slugger; that is, ballplayer is a word with a broader meaning than slugger:

Other hypernyms of slugger include baseball player.

slugger (noun)	ballplayer (noun)
(baseball) a ballplayer who is batting	an athlete who plays baseball
a boxer noted for an ability to deliver hard punches