\documentclass{article}

\usepackage{commath}

% Modified version of [this LaTeX Stack Exchange answer](https://tex.stackexchange.com/a/239823)
% by [John Kormylo](https://tex.stackexchange.com/users/34505/john-kormylo),
% © 2015 and licensed under [CC BY-SA 3.0](https://creativecommons.org/licenses/by-sa/3.0/).
\usepackage{scalerel}
\newsavebox{\unslantbox}
\newlength{\unslantdim}
\newcommand{\slantbox}[2][0]{\mbox{%
        \sbox{\unslantbox}{#2}%
        \unslantdim=#1\wd\unslantbox
        \hskip \wd\unslantbox
        \hskip -0.5\unslantdim
        \pdfsave
        \pdfsetmatrix{1 0 #1 1}%
        \llap{\usebox{\unslantbox}}%
        \pdfrestore
        \hskip 0.5\unslantdim
}}
\newcommand\unslant[2][-.25]{\ThisStyle{\slantbox[#1]{$\SavedStyle#2$}}}

\let\partialslanted\partial
\renewcommand*{\partial}{\unslant{\partialslanted}}

\pagestyle{empty}

\begin{document}

\begin{equation*}
  \dpd{f}{x} = x^2
\end{equation*}

\end{document}
