Does an archangel like Michael hear the dark prayers intended for Lucifer?

They do, indeed, hear the dark prayers, as they hear all thoughts of all humans. This is a function of their attention yet again. They do not listen to everyone simultaneously, but only focus on individuals of interest to them who are under their care, for example, or may be a potential adversary of someone reaching out to them in prayer. And so, they may be watching for an opportunity to use a request for healing on the adversary’s behalf, to go in and moderate things to benefit a person in need who is their victim. They do not eavesdrop on people, but, will act when asked to be of service. Whenever someone reaches out with a prayerful intent to the angels, all the angels hear the call, and then a decision is reached as to who will answer the call, for this always, always, happens. No one is ever ignored or refused a request. The only thing in the way of receiving angelic help is the limitations of the requester. That is always a rate-limiting step, not the ability or willingness of the angels to be of service. They answer many prayers at our request, and this indeed is a delegating of authority, for we are true to the intention of humans in all ways, at all times. If they reach out to God with their prayer, then to God it comes, and from us the answer is given, and this may well involve an intermediary in some cases. This is as it should be, because there are many worthy beings who wish to serve and are fully capable of carrying out many tasks, and to deny them the opportunity to serve is a form of disempowerment and dereliction of duty to support all beings in the highest and best way. So, it matters not to the one who prays who delivers the benefit needed, whether it comes from the hand of Creator, so to speak, or an angelic, or a friend or neighbor or loved one who suddenly wakes up to the need of the sufferer and comes to their aid in some way. What matters is the prayer is answered, and this is very much described in the Scriptures as the workings of God being mysterious and inscrutable, and the watching for signs and portents, and seeing acts of charity and fortuitous events and synchronicities as being God’s handiwork, for indeed this is often the case. We use every means at our disposal to restore balance and to right wrongs. All can participate in the divine work needed.