To compare frequency, we use adverbs like:
* Comparative: more often, less often
* Superlative: most often, least often
Examples:
* Comparative: He visits his parents more often than his sister.
* Superlative: Of all the students, Sarah attends class most often.
However, there are some cases where we might use "frequent" as an adjective:
* Comparative: This is a more frequent occurrence than in the past.
* Superlative: This is the most frequent reason for customer complaints.
But in general, when comparing how often something happens, we use the adverbs listed above.