The severability provision offered in the article I mention in this post includes the following phrase:
… provided the reason for the invalidity or unenforceability of a term is not due to serious misconduct by the Party seeking such compensation.
To which I say, “You cannot be ‘serious’!”
The word serious falls into that category of vague words and phrases that aren’t subject to a reasonable-person standard and so are in effect unusable. I just did a guest post (here) about another such phrase, moral turpitude. See also this post about substantial.
Where along the spectrum from trivial to really, really important does serious fall? I don’t know. That’s presumably why serious doesn’t appear much on EDGAR.
Another shortcoming of serious is that it has different meanings. In addition to expressing a level of importance, it also means “not joking or trifling.” I’m not sure which meaning is intended in the following extract from EDGAR:
In the event that there is an unsolicited proposal for or an unsolicited indication of a serious interest in entering into a Merger Transaction …
As for what to use instead of serious in the language that prompted this post, that’s not a simple question. A starting point in the inquiry might be this post about willful. In other contexts, material might be appropriate, as long as you remember that it’s not only vague but also ambiguous. (The most up-to-date discussion of that is in MSCD, but you can go here for my 2007 article on the subject.)