It's quite possible for entities (whether AI's, corporations or individuals) to at the same time perform valuable and useful tasks, while secretly pursuing a longer term, more sinister agenda.
And there's no need for it to be "evil", in the cliché sense, rather those hidden activities could simply be aimed at supporting the primary agenda of the agent. For a corporate AI, that might be maximizing long term value of the company.
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"AGIs make evil corporations a little eviller" wouldn't be the kind of thing that gets AI alignment into headlines and gets MIRI donations, though.