Mb zlych = angry? Why we use bad?
Zły is sort of a negative verb that contains bad angry and evil.
"Zły" is not a verb; it is an adjective, but indeed it has a whole range of meanings.
How would one say "I do not like the bad dog" (singular)?
"Nie lubię złego psa"
why is "mean dogs" not accepted?
Sounds good to me. Added "mean dogs".