He never did any of that. Thanks to the pure luck of Jenova falling into the Lifestream, he was able to use Geostigma. But since his form of the Lifestream never took over the Planet's, he never got to planet-moving power. Not even close. It's as irrelevant as Kefka planning to kill all life.

And can anyone tell me if Cloud's Omnislash is more powerful than a Light of Judgment? Said Omnislash owned Sephiroth so unless it equals city-destroying power, it's less than what Kefka can do.

And yes, refacing the planet is way more impressive than corrupting the Lifestream. It requires a bit more effort and since the Lifestream has ALWAYS been weaker than Jenova ie. Jenova has been stopping the Planet from fully healing for millennia, it's only natural Sephiroth's Negative Lifestream was winning.