'especially necessary' is correct and usable in written English.
You can use this phrase to emphasize the priority of a certain action or task. For example, "Making sure to continue wearing face masks and social distancing is especially necessary in order to avoid further spread of the virus."
This is especially necessary in the richer countries.
And it proved especially necessary when, in her mid-20s, she felt called to ministry.
"Those skills are especially necessary at WorldCom," said Stuart C. Gilson, a Harvard Business School professor who is an expert on bankruptcy and corporate restructuring.
The lessons taught in RE are especially necessary after leaving school, as we meet people from different backgrounds, traditions and religious beliefs from across the world.
As Einhorn might see it, people like him are especially necessary because so many others have been asleep at the wheel.
During his speech, the prime minister said that conservation efforts were especially necessary for the poor, who disproportionately depend on the ecosystem for their livelihoods.
The football match is especially necessary on Monday nights, when the regular television schedules have little to compensate for a first day back at work after a weekend.
A guidance system will be especially necessary if the well is to be put into production after the drilling platform is moved away.
While divorce ceremonies are important to the participants (or, at least, one of them), they can be especially necessary for the children of divorcing couples.
Antitrust and similar regulations are especially necessary in cases where certain market actors, such as companies, have acquired enormous market power.
Which means those unnecessary beauties are perhaps especially necessary.
