booktabs + tabularx + multirow + longtable — Professional Tables

CTAN: https://ctan.org/pkg/booktabs | https://ctan.org/pkg/tabularx
Manual: texdoc booktabs

Setup

\usepackage{booktabs}    % professional horizontal rules
\usepackage{tabularx}    % auto-width columns
\usepackage{multirow}    % cells spanning rows
\usepackage{longtable}   % multi-page tables
\usepackage{colortbl}    % colored rows/cells (optional)
\usepackage{siunitx}     % number alignment (optional)

Ugly vs Professional — Before/After

❌ Bad Table