I have one question. Is there something else other the betrayal by the 7 heroes? I was recommended by someone about this manga in this topic: http://www.mangaupdates.com/showtopic.php?tid=45919.

Does this manga answers any of my requests in that topic? I don't care about spoilers.

if you're asking whether or not Koinzell is betrayed by his current friends during his crusade against the 7 heroes, the answer is no

Quote from Andrez-ssi

if you're asking whether or not Koinzell is betrayed by his current friends during his crusade against the 7 heroes, the answer is no

Anything else?

Look at my topic and let me know if any of the criterias are met.

Yeah, it fits mostly, the betrayal by his closest friends is a back story that mostly happens in flashbacks. The manga itself focuses on his quest for revenge against his former friends who are now hailed as kings/heroes by taking the credit for his deeds and vilifying him as a traitor.

He's not outright evil but is a bit cold though does warm up to his new friends though he's not willing to harm innocents. He's also powerful. He was already known as the best among heroes before the betrayal and has only grown more powerful after his return years later.