Go back, turn back, turn around. All express this better than the given "walk back"
Go back or walk towards the back are okay, but turn around is unacceptable as a translation for this sentence, especially without the appropriate context.
I'LL BE BACK!
"Walk back" is ok in the context that you know it is a command.
For general context is should be "To walk back."
Walk back was marked as an incorrect translation for 往后 走 in a chinese to English exercise earlier, there it required us to say walk to the back.
往回走 might be a better translation here.
does this mean "walk back" as in walk backwards or just walk back to where you came from?