It may be that much harder to change to a more constructive behavior.
句中that应该是引导一个句子吧?但that 之后并无主语。如果是从句,那先行词是it吗?
It may be that much harder to change to a more constructive behavior.
句中 that 不是引导从句。
这个 that 其实是副词,表示程度,相当于 so。
句首的 it 是形式主语,后面的不定式 to change to a more constructive behavior 为真主语,原句相当于:
To change to a more constructive behavior may be so much harder.