\documentclass{standalone}

\usepackage{tikz}

\begin{document}
\begin{tikzpicture}

\draw(-3,0)--(3,0);
\draw(0,-1.5)--(0,3);

\draw[line width=1.5pt](-2.5,0)--(0,0)--(0,2.5)--(2.5,2.5);

\end{tikzpicture}
\end{document}

