Assuming a simple alkene such as ethene (\(\mathrm{C}_2\mathrm{H}_4\)), the major product of the reaction with \(\mathrm{KMnO}_4\) and \(\mathrm{H}_3\mathrm{O}^+\) would be acetic acid (\(\mathrm{CH}_3\mathrm{COOH}\)).
\[
\boxed{\mathrm{CH}_3\mathrm{COOH}}
\]