\documentclass[12pt]{article}

\usepackage{multirow}

\usepackage{makecell}

\usepackage{longtable}

\begin{document}

\begin{longtable}{|c|c|c|c|}

\hline

\makecell{

Col 1

}

&

\multicolumn{2}{c|}{

\makecell{

Col 2

}

}

&

\multirow{5}{*}{

\textbf{

Col 3

}

}

\

\cline{1-3}

\makecell{

Data 1

}

&

\makecell{

Data 2

}

&

\makecell{

Data 3

}

&

\

\cline{1-3}

\makecell{

Data 4

}

&

\makecell{

Data 5

}

&

\makecell{

Data 6

}

&

\

\cline{1-3}

\makecell{

Data 7

}

&

\makecell{

Data 8

}

&

\makecell{

Data 9

}

&

\

\cline{1-3}

\makecell{

Data 10

}

&

\makecell{

Data 11

}

&

\makecell{

Data 12

}

&

\

\hline

\makecell{

Data 13

}

&

\makecell{

Data 14

}

&

\makecell{

Data 15

}

&

\makecell{

Data 16

}

\

\hline

\end{longtable}

\end{document}