This of course is not an easy judgment since there are so many.
But after careful deliberation, I have to say that the worst Brazilian website I have read so far is:
Aventuras na História (Adventures in History)
I first found this website last year (see Histoganda) and I did try to contact them to correct the many factual mistakes they have made.
But of course, I got no response. In the meantime, the content continued to be as biased and flawed as it was. It actually got worse (if that is possible).
It is amazing, though expected, that this site is part of Editora Abril which in turn is part of the Folha Group, the largest media company in Brazil.
The problem obviously is not just the errors (factual, translation, cultural, etc) and anti-Americanism of the content. The real issue is that these articles are advertised as “history lessons”. I can imagine how many students refer to this garbage as fact and propagate all the half-truths and plain lies these guys managed to fit into their propaganda.
Is there an agenda here or just a large company pleasing the bias of its readers? I don’t know.
It’s a shame nonetheless.