He is a progressive that worshiped by many young people.从句是不是少个is

对的，少了一个is或者was
这里是that引导的定语从句，里边是一个被动语态，需要一个be动词，构成被动语态。
当然，假如不用is的话，可以处理成过去分词短语做后置定语，把that也去掉。这样就变成He is a progressive worshiped by many young people.