Procrastinational

From Futility Closet, a few years ago:

In the word ARCHETYPICAL, five letters occupy the same positions as in the alphabet — A is first, C third, E fifth, I ninth, and L twelfth.

Futility Closet, Ready Order

Armed with the knowledge that I have something else I should probably be doing instead, a copy of Python, and Ubuntu’s british-english-huge dictionary, I can now confirm that:

ARCHETYPICAL does indeed have the highest number of matching letters (five) for A..Z — a feat it shares with APODEICTICAL.
If we choose to align to the last letter instead, six words have five matching letters:

...IJKLMNOPQRSTUVWXYZ
       INOPPORTUNISTS
         OVERSTREWING
         OVERSTUDYING
         OVERSTUFFING
   THROMBOPLASTICALLY
       UNSPIRITUALISE

Reversing the alphabet to give Z..A results in one word with, again, five matching letters: JUXTAPOSITIONAL.
But by far the best result combines both: a word exists that matches six letters of the reversed alphabet when aligned to the end:

...SRQPONMLKJIHGFEDCBA
   PREPOSSESSINGNESSES