I have a chapter with sections and figures but now, I need the same chapter but translated to Spanish. What I did, in the same .tex, was to copy the content and paste after, i.e.

\chapter{Conclusions}
...
\section{...}
...
\begin{figure}
\centering
\includegraphics{...}
\caption{...}
\end{figure}
...

\chapter{Conclusiones}
...
\section{...}
...
\begin{figure}
\centering
\includegraphics{...}
\caption{...}
\end{figure}
...


I set \addtocounter{}{} to have the same numbering. However, this second part translated it shows in Table of Contents (ToC). I want to remove it from ToC without using, for instance, \chapter*{} or \caption*{} because I need to display the same numbering as before. Any idea?

\addtocontents{toc}{\protect\setcounter{tocdepth}{-1}}

at an appropriate point in your document will stop chapters being listed in the ToC. Similarly for figures {lof} instead of {toc} and tables {lot} instead of {toc}.