What is the best word to complete analogy seldom many as often to?

The best word to complete the analogy "seldom : many :: often : few" is few.

Here's why:

* Seldom means rarely, not often.

* Many implies a large quantity.

* Often means frequently, many times.

* Few implies a small quantity.

The analogy shows an inverse relationship. "Seldom" is the opposite of "often," and "many" is the opposite of "few."