Biblical prophecy, like religious history, is to be understood in terms of the message it is intended to convey. If taken literally, as in the first reading, with human sentiments and emotions projected on God, God would appear as harsh and as vengeful as the Assyrian king.
The evil we often experience proceeds from the negligent lives we humans lead. Thus, evil is a violation of justice, love and even of hope in our lives. Nevertheless, God uses human instruments, even tyrants, to mete out justice, which He always tempers with mercy in His call to repentance.
As Isaiah indicates, tyrants too, and whole nations have justice meted out to them in due course. People of faith attribute the final outcome to God. As Jesus declares in His prayer, it is childlike faith in God that enables one to discern God's action in both the events of history and in the personal lives of individuals. When I, for example, accomplish a task successfully, my awareness of my own powerlessness tells me that the glory of it belongs to God who has brought it about.
Lord, help me to lead a life of God-awareness so as to be joyful in Your ways always. Amen.