The game designer has gone on record as stating people around level 18 or so would be potential planet busters; anything higher, no problem, easy.
One reason the planet doesn’t get squished, is that these guys don’t fight often, fight each other less-often, and when they do they’re hitting each other, not the planet.
Also, outside of two characters, the most potent people work for Imperium, the nebulous organization in the shadows (incompetently) overseeing everything. Ie, the guys Noldere is talking about.
But the game is pretty high powered; at level 4, my character in Siriel’s game had a Dominion Technique mastered that could - and did - annihilate a swathe of an army. Had the army been grouped, and not surrounding a city, she might have got them all. Granted, she’s somewhat of an outlier, but not THAT big of one.
On the Anima forum, someone asked ‘If Kisidan and Nerelus (two of the most powerful ‘normal’ name level people, who are nonetheless only level 14) fought, who would lose?’
Official answer was ’The country in which they fought.’