So that's what you meant by "city-buster." I was referring specifically to destructive properties in spell comparison.
Cerma > Thunder Palace in destructive power.
Also, pretty much every spell that causes destruction in any shape or form has more destructive power than Fairy Law. Fairy Law is, in that regard, like an Avada Kedavra.
Assuming it's as powerful as Shakuma's, yes. But Fairy Law matches or surpasses it in terms of range.
And Avada Kedavra's a pretty useful spell. Gets the job done without many fancy lights and sounds and unnecessary collateral damage.
There is nothing to suggest the bold. You're completely disregarding what Erza said about Fairy Law back in the Phantom Lord arc.
Mashima is free to contradict himself whenever he wants, but until he does so, those quotes regarding Fairy Law are very much relevant.
Never mind what Erza said. The commentary in the Fantasia Arc as well as Hades' statement in the Tenrou arc make it clear Fairy Law eliminates those the caster sees as an enemy, right of wrong.
No contradiction there. We even saw it validated with Laxus failing because despite his rebellous actions he still cared for Fairy Tail deep down.