This is not the most mispronounced word in the English language as someone defined it. According to Longman Pronunciation Dictionary, the word "often" can be pronounced with the "t" (like off-ten) or without the "t" (oh-ffen).

Many speakers use both the form without t and the form with it. Preference polls. Br. no t 73%, with t 27%. American English, no t 78%, with 22 %. (Longman Pronunciation Dictionary).

This is one of the most mispronounced words in the English Language. It should rhyme with "coffin". It isn't "off-ten".