Q:

Writing a bad review in a tactful way

I have a blog which sometimes features bad reviews based on my personal research and point of view.
Please help me know how to say something critical without being too hurtful. For example, the object is a piece of software, but when I use it and check it, the software contains malware and I tell my readers about it. 
If you have a bad experience, and know about it, what are you supposed to say to your readers?

A:

Your example is a bit extreme but in general:
Highlight the successes as well as the failures.
Try to express understanding and sympathy for how the failures might have occurred. For example perhaps you point out that something is a first effort, or the budget was a little low, or some other factor out of the control of the author/developer/filmmaker.
Avoid attacking anyone personally, or trying to judge a person or organisation based on what you think are the product's failings.
If there is a serious problem, eg a software application doesn't work or contains malware, contact the person or organisation asking for their comments and assistance and and recount that exchange alongside the review.

