Doitsu Gun Shoukan! ~Yuusha-tachi ni Subete o Ubawareta Dragon Shoukanshi, Moto Saikyou wa Fukushuu o Chikau~

Summary

Dragons are the strongests. The ones that employs dragons are the strongests. The ones that kills dragons are the heroes. The one who kills those that kill dragons would certainly be… Nasser Virginia was once the most powerful dragon summoner in the world, however the hero not only destroyed his spell mark (呪印) which is necessary to summon dragons, but also cuckolded his wife. Betrayed by the citizens, the church, and even the guild master, Nasser loses everything. However, despite being under such circumstances, Nasser did not give up on getting his revenge against the hero. This is the story of the former strongest becoming the worst avenger of all. …What did their actions create? No one knows yet.