Honestly, I don't see why we didn't outright downgrade this feat quite a while ago.
Thaddeus orders
Space Racer to fire his gun, a weapon that can obliterate Viltrumite War Invincible-level characters and blast through stars, at Viltrum to destabilize its core. If the
core were to become stable, they'd die on impact. After
the impact, we see
secondary explosions all over Viltrum's surface, and the planet
takes time to break apart and
explode once they pass through the core. In real life, planets like Earth do not have any internal mechanisms to violently explode, but this is fiction.
So all in all, Invincible, Mark and Thaddeus demolished Viltrum's already unstable core in perfect sequence, causing the entire planet to be destroyed. The fact that there's absolutely no
Planet level feats or statements (literal or non-civilization statements, anyway) in the series further reinforces my point.
I did a calculation of the crater the three made, which gets
Multi-Continent level results per person. It hasn't been evaluated, but I'm hoping this thread will garner some traction because I've been asking for a while (so far two staff members have commented).
Also, I'm pretty sure this
GBE is wrong. Surface gravity is actually inversely proportional to radius when density is fixed, not directly proportional to mass.
Gliese 581 and Jupiter (or just gas giants, for that matter) are very good examples of this.