"Germany is definitely different from Brazil."
Translation:Definitivamente, a Alemanha é diferente do Brasil.
Yes, you need it here. It's the one and only Germany.
You could write it with no articles if you removed it from Brazil too: Alemanha é diferente de Brasil. (In this case you are not really talking about THE coutries, but rather types/characteristics of countries labeled by their names)
I don't believe you can omit the article. At least not in a normal sentence. Only if you are trying to put Brazil as some idea or a thing, but not when referring to the country. I'm not sure if this explanation is ok, but....
In Portuguese, most countries always use an article. Portugal is one of the few exceptions.
The rules change for each country, but for a single country, it's steady. If a country uses an article, it always uses it. If not, it never uses it.