weakness vs tough luck

weakness and tough luck both are nouns.

Word	Noun	Adjective	Verb	Adverb
weakness	Yes	No	No	No
tough luck	Yes	No	No	No

As nouns, tough luck is a hypernym of weakness; that is, tough luck is a word with a broader meaning than weakness:

Other hypernyms of weakness include bad luck, ill luck, misfortune.

weakness (noun)	tough luck (noun)
the property of lacking physical or mental strength; liability to failure under pressure or stress or strain	an unfortunate state resulting from unfavorable outcomes
powerlessness revealed by an inability to act
a penchant for something even though it might not be good for you
a flaw or weak point
the condition of being financially weak