skill scaling, Ultimate Move 'breaking defense'

[Yeezus]

Utimate moves description "if not/if breaking defense", what does that mean?

And about scaling, is externals still good on allies if it scales with Protagonist Stats
like Benevolence,Righteousness,etc?

For sword i'm mainly raising stats to be 10-15 except luck, and the rest on int. I assume that too much dex is too bad esp with action speed traits. For fist would more str be good rather than int? but Intelligence traits at 10 or 25 are so good,and better Atk/Defense growth too.
Edit: I just read that to beat endgame bosses you have to go for certain strategies like bleed and big health, other with damage reduction.