Create big fat green arrow like in excel

You could build your own.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{shapes.arrows}
\newcommand{\FancyUpArrow}{\begin{tikzpicture}[baseline=-0.3em]
\node[single arrow,draw,rotate=90,single arrow head extend=0.2em,inner
ysep=0.2em,transform shape,line width=0.05em,top color=green,bottom color=green!50!black] (X){};
\end{tikzpicture}}
\begin{document}
ABC \FancyUpArrow\ DEF

{\Large ABC \FancyUpArrow\ DEF}
\end{document}

This is a simple construction of a big fat green arrow using Mathcha. By changing the scale parameters you can construct an arrow of different sizes depending on the size of the character which is not automatic.

\documentclass{article}
\usepackage[dvipsnames,table,xcdraw]{xcolor}
\usepackage{tikz}
\tikzset{every picture/.style={line width=0pt}}
\newcommand{\bigfatgreen}{\begin{tikzpicture}[x=0.5pt,y=0.6pt,yscale=-.5,xscale=.5]
\draw  [fill=ForestGreen!70,fill opacity=1] (100,123.22) -- (113.25,113) -- (126.5,123.22) -- (119.88,123.22) -- (119.88,138.54) -- (106.63,138.54) -- (106.63,123.22) -- cycle ;
\end{tikzpicture}}
\begin{document}

\begin{table}[]
\centering
\begin{tabular}{|l|l|l|}
\hline
\rowcolor[HTML]{C0C0C0} 
\multicolumn{1}{|c|}{\cellcolor[HTML]{C0C0C0}\textbf{Item}} & \multicolumn{1}{c|}{\cellcolor[HTML]{C0C0C0}\textbf{Mean}} & \multicolumn{1}{c|}{\cellcolor[HTML]{C0C0C0}\textbf{Variance}} \\ \hline
1                                                           & \bigfatgreen\, 1,3                                                        & 1,0                                                            \\ \hline
\end{tabular}
\end{table}

\end{document}

The pifont package has all kinds of nice arrows:

\documentclass{article}

\usepackage{pifont}
\usepackage{xcolor}
\usepackage{graphicx}

\begin{document}

foo \rotatebox{90}{\color{green!80!black}\ding{225}} bar

\end{document}