When we talk about "hard eyes", we usually refer to a particular gaze that conveys toughness or sternness. This can be useful in certain situations, but it is not always appropriate. Fortunately, there are plenty of synonyms that can be used instead. For example, you might use words like "firm" or "steady" to describe a gaze that is determined and focused. Alternatively, you could use words like "unwavering" or "unblinking" to convey a similar sense of strength and intensity. Ultimately, the key is to choose your words carefully and thoughtfully, so that you can convey the right mood and tone in your writing.