The light side has been and always be stronger than the darkside.

1. The force likes the lightside more

Lucas has stated the darkside is a cancer to the force. So obviously the force would side with the lightside. Also the force is unkillable so the darkside will eventually lose. The force also has no patience for the darkside and therefore created the most powerful force user of all time, anakin for the light when sidious and plaguies tried to shift it to the dark. Anakin was an unassuming double agent slightly accelerating a purge that was going to happen before giving the rebellion everything they needed to win(palps death, luke, leia,starkiller,ahsoka tano).

2. Force users.

The light also has the most powerful force users, gm luke, and yoda, with emp sidious the only one on that level. The most raw powerful is also a force user and he was at his most powerful(as a jedi). The skywalkers the most powerful guys in the galaxy were created for the light always end up lightsiders.

3. The flaw in sith philoshophy

Sith are under the ridiculous impression they can control the force, or in other words god. THEY CAN'T. Prime example, sidious and plague try to make the force dark, force pimp slaps them giving the lightside the most powerful force user ever and a family that kicked sith butt for millenia.

4. Galactic History

Its pis and good guy syndrome, but the in universe explanation for the jedi almost always winning is as yoda says, the dark side can only destroy. The darkside cannot preserve crap as there will always be some civil war every damn decade. The lightside has kept control for millenia at a time. The only time the sith ever won was in rots and even then it was the jedi who technically won the clone wars.

4.Powers

Most powerful powers are light side. Most powerful ability immortality(true immortality unlike spirits and such) are stated by those who give immortality to be only attainable by jedi. So yea either darth marr redeemed himself vs the emperor or him being a force ghost was completely non canon.

The second most powerful ability, oneness, is exclusively lightside.

The third most powerful ability sever force is totally lightside

I rest my case, all sith punks need to be force choked

@shootingnova@alextheboss@dadivineking