I don't believe you are going to be able to do this through a simple filter. If you filter for incomplete tasks task 2 in your example will disappear.

It may only be possible through code. You'd need to loop through each summary task and if out if it is 100%, if not show, set a flag for all its children. The filter on the Flag.

I don't write code so I can't help much further than pseudo code. Try posting your question to :

https://social.technet.microsoft.com...ct2010custprog

Please explicitly state (as you did in this post) what version of Project. Please also be so kind as to come back here and create a post with the link to your question in the Microsoft Forum so that others may follow along.