When do I omit the 'the' and when I can't

X is the second most intense quake and [the] most powerful since 2000

X is the most intense quake and [the] most powerful since 2000

Thanks

I think the second "the" is optional in your second example. If you use "the" once, it applies to both "most intense" and "most powerful," which are parallel. For that matter, you could phrase it this way:

X is the most intense and powerful quake since 2000.

The single use of "the most.....quake" applies to both "intense" and "powerful," which are parallel.

I think you do need the second "the" in your first example, as "second most intense" and "most powerful" are NOT parallel. Without "the" in front of "most powerful," the parallelism might be interpreted two different ways:

X is the second most intense quake and most powerful since 2000.
could mean
(1) X is the 2nd most intense quake and X is the 2nd most powerful
(2) X is the 2nd most intense quake and X is the 1st most powerful.

That said, I prefer to repeat the "the" in both of your examples, as it emphasizes the parallelism. Writers will often repeat words when not strictly required, as doing so fosters clarity.

At the animal shelter, we need donations for utility bills, especially during the summer months when expenses are high, for medical supplies, and for food.

Repeting "for" three times makes it easier to understand that we need donations "for" three things.

_________________
Emily Sledge
Instructor
ManhattanGMAT