Drawing a backward arrow in a flow chart using TikZ

Based on my answer on your previous question. Feedback arrow is drawn in two parts: from the last node F to aux coordinate placed above node C and from it to the first node A:

draw[arr]  (F) |- (aux) -| (A);

For this is defined new style arr which is used in above command and in every edge style (used for drawing connections between nodes). In the below proposed solution is not used resizebox, rather are reduced node distance and text width of nodes:

documentclass{article}
%---------------- show page layout. don't use in a real document!
usepackage{showframe}
renewcommandShowFrameLinethickness{0.15pt}
renewcommand*ShowFrameColor{color{red}}
%---------------------------------------------------------------%
usepackage{tikz}
usetikzlibrary{arrows.meta,
                positioning,
                shapes}

begin{document}
%centering
    begin{tikzpicture}[
  node distance = 2mm and 8.8mm,
     arr/.style = {draw=black!50, thick, -Latex},
    base/.style = {draw, font=small,
                   minimum height=2em, text width=4em, align=center},
   block/.style = {base, rounded corners, fill=#1},
 block/.default = white,
decision/.style = {diamond, base, inner xsep=-3pt},
decision/.default = white,
every edge/.append style = {arr}
                    ]
node [block] (A) {Initial step};
node [block, right =of A] (B) {The next step};
node [block, above right = of B] (C) {The third step};
node [block, below right = of B] (D) {The fourth step};
node [decision, below right = of C] (E) {Is condition met?};
node [block, right =of E] (F) {The an action};
%
coordinate[above=of C] (aux);
path   (A) edge (B)
        (B.+5) edge (C.west)
        (B.-5) edge (D.west)
        (C.east) edge (E.north west)
        (D.east) edge (E.south west)
        (E)      edge (F);
draw[arr]  
        (F) |- (aux) -| (A);
    end{tikzpicture}
end{document}