feedback is always subjective. This is the main difference between feedbakc and assessment. The latter is based on objectives, criterias, measures and indicators. In feedback you refer to your personal experience, observation, opinions, emotions. You use sentences with "I think", "In my opinion" to emphasise the perspective.

It is important to focus on only a few most important issues that can be valuable to the person you give feedback to. Abundance of information can be overwhealming and discuraging. Select 1-2 main points that can be improved. Begin and end your feedback with a distinctive positive remark. Describe what is good and important - positive feedback is an energiser that stimulates development. Aknowledge it.