"Opposite of" is used to differentiate the essence or the main features of two things: "Bad is the opposite of good", "Big is the opposite of small". "Opposite to" is used to express that two things are physically located in opposite places or facing each other.

Example: The opposite of white is black. Example: White is the opposite of black. You use "the opposite of" to tell us what the opposite of something is. You us "opposite to" a little differently. Example: The effect was opposite to the effect they wanted. It's hard to explain the exact difference. When you use it this way, it's more like something that contradicts something else.

thanks