What is the subject of sentence with ください?

Question

For example, what is the subject of the following sentence?

八時に来るようにしてください。

The speaker or the opponent?

Answer 1

Hope I've understood you correctly:

くださる means 'to give'.

(You) give (me) the favour of making sure to come at 8 o'clock. = Please make sure to come at 8 o'clock

The person doing the giving (you) is the opponent which is the subject of くださる. The speaker (me) is the indirect object.