Granted. Still, When The Psychos Come Calling ...
UltraSeven, in his original series, had a few bad days. One of those days was having to deal with extremely smart aliens (OK MOST of those days) that knew he was weak to extreme cold. So they knocked it down to Ice Age temps and froze him to near death. By the time he transformed, he was in no shape to fight their monster, and had to replenish his strength quickly.
So he flew into the sun for a few minutes, came back to Earth and murdered the hell out of their plans.
A small note. Ultraman Jack, when fighting Bemstar, would attempt the same feat. However for one reason or another he couldn't handle it, and had to be saved from the sun by, you guessed it, UltraSeven.
And at the end of Ultraman Leo's final episode, Black, as a suicide manuver, sent his planet to crash into Earth. So Leo blew it the hell up.
Thus yes, Leo destroyed a planet. Maybe not a large one, but hey.
Of course years later we'd see that destroying large bodies in space is trivial in the grand scheme of things, as in Ultraman Mebius two different Earth shattering meteors were easily dealt with by two different aliens (Zamashu and Ultraman Mebius) in two different episodes.
As for why their enemies do not inflict carnage on that kind of scale, it's likely because they have no reason to. Almost all of them, in their plots and plans, need the Earth intact or at least want it to be so, and some of them even want humans mostly unscathed.
In the Ultraman Mebius movie, Yapool even used this to his advantage, having U-Killersarus park itself in front of the Earth, so that the Ultras wouldn't get the bright idea to combo beam it to death. .....mind that didn't work, but hey, it gave them pause.
And yes, DBZ stands for Dragon Ball Z.
Thanks for the additional info on Ultraman Leo's ending; Wiki didn't have those details ... :disappoin
Granted, the vast majority of villains don't want to do too much large-scale damage and destruction. But, it seems that, sooner or later,
somebody shows up who is seriously into just that.
Like Ghatanothoa, who covered the entire planet in a toxic darkness that forced GUTS to evacuate the Citagon, and forced the population into shelters. Not to mention overwhelming Tiga in the first re-match ...
Then, there was the dear GranSphere who "outed" Asuka to a renegade group of TPC officials so he could be killed. And when
that got thwarted, it "outed" him again - to the entire Earth, demanding that he surrender to it - or Earth ends up as dinner ... (Or so it seemed to a non-Japanese listener. If I'm wrong, don't hesitate to correct me.)
And, dear Zogu. Who sent a "death god" to neutralize the newly-reborn Agul by kidnapping his girl friend, lures X.I.G. into a battle that they can't win so it can capture Gaia, forcing Commander Ishimuro to destroy his beloved Aerial Base to win the battle. And then, after it blanketed Earth with a swarm of light-absorbing mini-monsters, it has the
utter nerve to appear on Earth as an "angel" before killing Gamu and Hiro's Ultraman forms.
Finally, when Emperor realized humanity would willingly sacrifice itself to stand by Mebius , despite the overkill of
thirteen Imperizers all over the world; he decided to "black out" the Sun itself while he dealt with Mebius. Poor dear didn't realize the Space Garrision would turn out in force to take out his schemes - and then
him.
My point is, if those attacks hadn't been defeated quickly, especially the latter two, the enviromental damage would have been horrendous, causing mass extinction events. Only in Dyna did Earth escape unscathed - and then, at a terrible cost ...
Or
did it escape unscathed, after all?