I heard this on television yesterday.

Problem:
The adverb “back” in “return back” is redundant.

Explanation:
The verb “return” means to go back, so the meaning of “return back” would be to go back back.

Because the “re” in “return” means back, one could argue that someone who “returns back” would never reach the intended destination.

For fun, I searched Google for the expression “return back” (with the quotation marks) and got about 2,490,000 matches. This is depressing.

Solution:
“return”