The phrase "a bad core" is correct and usable in written English.
It can be used to describe a fundamental issue or flaw in a system, organization, or concept.
Example: "The project's failure can be traced back to a bad core in its initial planning stages."
Alternatives: "a flawed foundation" or "a weak core".
She sought to mask her deficits -- an almost nonexistent low register and an inability to reach the top notes -- with a certain amount of vocal swooping, while she tossed her head from side to side like a bad soft-core actress.
Feeling like you're just a bad person at your core can undermine efforts to change, as change may not even seem possible from this perspective.
It was a bad job for hard-core idealists, most of whom ended up frustrated and unhappy.
It makes me wonder if he's noticed that it's already created a bad bank, known as 'non-core', with assets it has been selling and running off on an unprecedented scale, already shrinking its balance sheet by £900m.
But there's something unconvincing about her explanation of why, at its core, this is a bad idea.
Each story centered on the efforts of the exuberant and wildly imaginative "greatest hero ever" to save the lazy Manfred from villains like Crabby Appleton, a meanie who was "rotten to the core" and did a bad deed every day.
"Incentive schemes on PPI were rotten to the core and made a bad problem worse," said Martin Wheatley, managing director of the FSA, the City watchdog, in a recent speech.
"There's nothing to be gained from passive observance, the simple documenting of conditions, because, at its core, it sets a bad example.
You will also need a regular concealer, go hard core if you have a bad pimple,or more than one.
"The core message is not that Barack Obama is a bad guy," Mr. Rath said.
