The major product of the following reaction is:

Alkaline $\mathrm{K}\mathrm{M}\mathrm{n}\mathrm{O}4$ oxidise benzylic carbon to the carboxylic acid.

Alkenes react with acidified potassium permanganate. Potassium Permanganate is a strong oxidant, and will initially convert the double bond to two alcohol (OH) groups.