@Pat347 What you should be more scared of is past reviews for guests who want to book with you that aren't honest and make you think the guest will be okay when in fact they were terrible guests and the hosts were scared to say that.
No, guests can't see the stars you leave them. And they can't read your review of them until both reviews are submitted, or, if the guest doesn't leave a review, your review of them will be posted 14 days after check-out. And then it is too late for the guest to leave a review at all. So they can't write a bad review of you just because you left a bad one for them- they can't see it until it is publicly posted.
Reviews don't have to be either completely good or completely bad. There is usually something positive you can find to say about a guest (unless they were just awful people all around) while mentioning the things that made them less than desirable. "XX was a good communicator during the booking process and pre-arrival, and quite friendly. However, his failure to thoroughly read the listing description and understand what he was booking and to follow house rules made hosting him quite a challenge. More attention on this guest's part in the future as to the type of listing he is booking, as well as showing respect for house rules, would lead to a better host/guest experience."
Writing a review along those lines lets other hosts know the downsides, lets the guest know what areas he needs to improve in to be a welcome guest, and hopefully tells the guest that you are being fair, in that you also recognized his good qualities.
If a guest is just really bad, though, don't try to sugar-coat it- no one wants a guest who has uncaringly made another host's life miserable.
And if a guest has been truly awful, wait a few days or a week to write a review if you're feeling mad or upset about it. That gives you time to get over it a bit and not be tempted to leave an emotional review- instead you can compose your thoughts and just write something brief and factual.