Gryffindor: Unavoidable- there is no terrible thing that cannot be solved if everyone involved is willing to examine their behaviour and change themselves or fight back.

Ravenclaw: Unsolvable- keep pushing, keep innovating, find new solutions to old problems and mysteries

Hufflepuff: Unfixable- With patience and a willingness to put in the work required, almost anything can be repaired- dilemmas and problems can all be worked through

Slytherin: Impossible- just because it's never been done, doesn't mean you can't do it.