Yuji is a young businessman with a penchant for groping women on the train. Unfortunately, he's really bad at it... His hobby is about to land him friendless, homeless, and probably behind bars. Enter the dashing hero, Kazuo, the man with the Golden Touch, any woman he touches turns to be horny!

What is the most one sided battle scene in an anime series?

The Battle of Arnus Hill would be a good candidate.
In these successive offensives from Gate: Jieitai, a massive medieval army, numbering hundreds of thousands of soldiers, marches against an advance force of the Japanese Self-defense Force which occupied Arnus Hill after a gate to the centre of Tokyo opened there. The generals are confident they can quickly defeat this small force which defiled their sacred hill.
So they march on the entrenched Japanese.
But, as soon as they enter the prohibited zone, the JSDF opens fire.
Between motorised artillery, MBTs, heavy machineguns and the infantry with their assault rifles, the allied kingdoms don't stand a chance.
About 10.000 soldiers are killed as the rest flees. And yet, they decide to try it again, with even worse results, an estimated 40.000 lost.
After seeing the results of the previous attacks, one of the generals decides to strike under the cover of darkness. As you might have guessed already, that doesn't go very well either.
The soldiers quickly find themself out in the open with flares burning as bright as the sun.
Another 20.000 soldiers are butchered by the overwhelming firepower of the JSDF. In the end, the armies of the allied kingdoms are pretty much annihilated, and are no longer capable of participating in any wars.
A single arrow was fired at the JSDF, but it most likely did not hit anyone. The JSDF killed roughly 70.000 enemies without losing a single soldier.
It doesn't really get much more one-sided than that if you ask me.