Mimicry

Mimicry is the power to copy any power and use it as your own. The 17th century warlock Matthew Tate has this power, he was the lover of Melinda Warren and tricked her. In doing so, he was able to copy her powers and told evereryone in Salem that Melinda is a witch. After someone uses their power on him, that person's powers won't work against him anymore. This grants him complete immunity.