Life's greatest regret,THAN the wrong insist,and easily give up. So what does the "THAN" here mean?

I think that 'than' is a misprint for 'that'. The whole sentence, in fact, is not very clear, to the point of being generalised nonsense. I would understand the whole sentence to mean something like: "[One of] the greatest regrets in life [is that] the wrong (using the adjective as a noun to mean 'people who are wrong in their thinking') insist (perhaps, meaning that they assert something strongly) and then easily give up." Perhaps it refers to the kind of people we have all encountered who shout very loudly about what they believe to be right but, when they are challenged about their views, tend to become silent because they are unable to defend them.

Did they mean to say "that" instead of "than"? This whole quote is confusing.

we can understand well if we can get where you cited it from. maybe you just want to say:Life's greatest regret,( no more )THAN the wrong insist,or easily give up.