Learn Turkish: Bu haber herkesi sarsacak kadar kötü. - This news is bad enough to shake everyone.

The word kadar usually means "as much as" or "up to." When you attach the future suffix -AcAk to a verb and follow it with kadar, it creates the meaning "to the degree that it will do [action]." Here, sarsacak kadar literally translates to "to the extent that it will shake," which is exactly how Turkish expresses "enough to shake."

Why is it herkesi with an -i at the end, rather than just herkes?

Herkes (everyone) is the direct object receiving the action of the verb sarsmak (to shake). Because pronouns and words like "everyone" are inherently specific, it requires the definite accusative case ending -i.

Why is the phrase for "enough to shake everyone" placed before kötü (bad)?

Turkish is strictly a "modifier before modified" language. The entire clause herkesi sarsacak kadar acts as an adverb describing exactly how bad the news is. Therefore, it must sit directly in front of the adjective it describes (kötü).

Where is the verb "is" in this sentence? Should there be a suffix on kötü?

For third-person subjects like bu haber (this news), the "to be" suffix is usually dropped in everyday Turkish. While you might see kötüdür in formal writing, just ending the sentence with the adjective kötü is the most standard and natural way to say "is bad."