seriousness

I don't think he has any idea of the seriousness of the situation.

我认为他一点儿也不明白形势的严峻性。

In all seriousness now (= I am now being serious and no longer joking), I do think there's a problem here that we need to straighten out.

现在说正经的——我确实认为这儿有个问题我们得解决。