I am looking for a quote from a figure of importance at the time who expressed their desire that Europe should avoid any such violence in the future, something which sums up the general feeling of waste at the end of the war.

You're probably best off looking into the allied leaders in Paris, especially with regards to the League of Nations, since the hope was that that organization would serve as a forum for settling and arbitrating international disputes.

However, I would question your assumption that the 'general' feeling was one of waste. Suffice to say, millions of people that had been involved in the conflict looked on it in different ways, and not all of them were wholly negative, and some were rather ambiguous. Among many of the Allied soldiers, you'd probably find feelings of relief and even disillusion, but also no doubt some pride at what they had done. In Germany you'd find those that wanted nothing more than to put the war behind them, and others that would call for another war to restore Germany's position.

I'll suggest one, a quote that Kathe Kollwitz used in the German SDP's newspaper Vorwarts, from Goethe: "You must not grind the seed-corn."