The superlative of "often" is "most often."
most often is the superlative degree for often
OFTEN
Dative; Early Comparative; Earlier Superlative; Earliest
more often, most often
Most often
more often, most often
more often, most often
more often, most often
more often, most often
more often, most often
The comparative form of "often" is "more often," and the superlative form is "most often." Since "often" is an adverb that indicates frequency, these forms help express varying degrees of frequency in a comparative context. For example, "She visits more often than her friend," and "He visits the most often of all."
Comparative: More oftenSuperlative: Most oftenmore often, most oftenmore often, most often