It might be Procter & Gamble that makes the most washing powders.
It seems to me that the sentence means the number of washing powder trademarks offered by Procter & Gamble – not superior properties of these washing powders, and therefore “the” is redundant here.
Source: “Objective IELTS Advanced” ("Grammar folder" - So the sentence comes without context.)
In your example,
- “the most washing powders”
Means nobody else makes more washing powders — they are the #1-ranked company.
For every 100 packages that are sold, they sell the highest number.
- “most washing powders”
.. means they make the majority of all of them. Nobody else makes a lot.
For every 100 packages that are sold, they sell at least 51 of them.
Most is used to form the superlative of many adjectives and adverbs:
- Joanne is the most intelligent person I know.
Most also means almost all:
- I like most vegetables. — Cambridge Dictionary