Should be marked as bullshit. But I guess

W = mad

says it all.

Just look at W = mad, and calculate the distance d a body travels when there is a constant acceleration (mass of the body does not play a role here) applied to it over a time t starting at zero velocity up to a final velocity v. You will find the 1/2 there, as that turns out to be d = 1/2 v t. So you have (with a = v/t) W = m a d = m a 1/2 v t = m 1/2 v².

Furthermore E = mc² is not kinetic energy, it is energy of the mass at rest. The complete relativistic energy equation is E = sqrt((mc²)²+ p²c²) with p being the momentum of the body. A body at rest has p = 0 and so no kinetic energy at all, which gives the famous

E = mc².