"The best defense is a good offense."
Translation:A melhor defesa é o ataque.
This is the kind of translation which is designed to steal a heart :-)
There are a number of issues (particularly if you speak British English). The main one is the loss of the adjective "good" in the translation. It is tempting to use the word "ofensa" but I think that is a false cognate. The indefinite article in "a [good] offense" has been replaced by the definite article in "o ataque'.