Answer
If we attentively hear and chant the Hare Krishna maha-mantra, we receive the full spiritual potency of the Holy Name.
Black magic certainly involves a kind of power, but it is a tamasic (mode of ignorance) power. However, the Supreme Lord is the source of all power, and His complete spiritual energy is Srimati Radharani.
When we sincerely chant:
Hare Krishna Hare Krishna Krishna Krishna Hare Hare
Hare Rama Hare Rama Rama Rama Hare Hare
and strive to please Radha and Krishna, black magic cannot ultimately succeed against us.
Everyone in this world has free will. Just as someone may try to push you while you are walking, similarly negative forces may attempt to influence a devotee. But if you possess spiritual strength, those attacks cannot shake you.
In the same way, black magic may attempt to affect a devotee, but a spiritually strong devotee remains undisturbed.
Regarding Bangladesh and other demonic governments, our response should not be to curse people. Rather, we should all come together and chant sincerely so that we become spiritually powerful.
Every person has the opportunity to become a powerful sage. Srila Prabhupada wrote that the soul is extremely powerful.
If we chant casually simply for our own protection, Hari-nama will certainly protect us. But if we want to help and transform the world, we must become spiritually powerful through deep and sincere chanting.
This is how Krishna's movement will spread. Miracles can happen. Srila Prabhupada himself demonstrated this by single-handedly inspiring and transforming people all over the world.