An aggriever is a person who aggrieves - who gives pain or sorrow to someone, or who oppresses one's rights.
An aggrievance is an instance of hardship, oppression or injury.
There isn't any proof. AT ALL! We can only make things improve or make things worse. We can not make evidence. There is no evidence at all that says things will inprove or worsen. There is only hope and doubts. It is famously qouted by Hazrat Ali (RA), which sense like, "Society can run with the Kufr (deny of existence of God) but it can not run with aggrievance." So that decline of society belittles the chances of improvement.
There are 6,571 words like that in Webster's Second International. Here are the first 100: abalienate abalienation Abbie Abdiel abeigh Abie Abies abietate abietene abietic abietin Abietineae abietineous abietinic Abiezer abortient abortifacient absenteeism absorbefacient abthainrie Acadie Acanthodei accidie accipient accompanier acetifier acetothienone acetylenediurein acetyltropeine acheilia acheilous acheiria acheirous acheirus achievable achieve achievement achiever Achilleid achilleine Achromobacterieae acidifier acier acierage Acieral acierate acieration Acipenseroidei acleidian acleistous Acmaeidae acneiform acquiesce acquiescement acquiescence acquiescency acquiescent acquiescently acquiescer acquiescingly acraein Acraeinae Acrasieae acrolein acropoleis actifier actinodielectric acturience aculeiform adagietto Addie Adeleidae Adiel adieu adieux Adigei adoulie Adrienne advenience advenient aeolsklavier aerie aeried affeir affreight affreighter affreightment afield afterfriend aftergrief afterpiece Aggie aggrievance aggrieve aggrieved aggrievedly aggrievedness aggrievement Agiel agonied