(they are a convicted monopolist after all)
I'm not sure that being a monopolist is any kind of crime, so being convicted of such a thing does not seem possible? However, I have seen such language here before and I would like to emphasize that they were convicted of being monopoly abusers, as in.. they abused their fully legal monopoly position. I feel that there are different possible PR angles around these terms, and it is important that we do not encourage that.
convicted monopolist: the implication can be promoted that its not really their fault that they are so popular that everybody uses their products and the EU really is unfair to penalize them because of that.
convicted monopoly abuser: this is much more difficult to weasel out of, as it has the negative word abuser in the phrase.
Personally, I prefer the latter phrase as it is more descriptive and correct, and I feel it is important to label such a company as this correctly, so that other people who would otherwise not know the details, are not as able to be misled..