Will a person be held accountable for the whispers of Satan that involve wishing ill upon others, whether he articulates them and then regrets it, or does not articulate them, and how can one get rid of them permanently?

If the evil thoughts are merely whispers that you reject, then there is no harm in them and no sin, for the Prophet, peace and blessings be upon him, said: "Indeed, Allah has pardoned for my nation what they whisper to themselves, as long as they do not act upon it or speak of it." And if you utter something of it unintentionally, there is no sin upon you. However, continue to strive against your soul by supplicating to divert these whispers from you, and remember that the perfection of faith is achieved by loving good for Muslims, as the Prophet, peace and blessings be upon him, said: "None of you truly believes until he loves for his brother what he loves for himself."