Glasscannon, meaning that a person/weapon/vehicle or whatever has high output of damage or/and long range but has low defense. Basically, I want MCs like can destroy one or two countries with an attack but a punch or two will take them out. I'd prefer if they're mage or something similar. Things that I don't want: Cocky mc. Really dislike it. Unless if the mc is like "not gonna save you if you get into trouble" but proceed to save the said person anyway when they're in trouble type of cocky mc. You know what I'm saying?
Havent really seen Konosuba other than a few manga chapters and isekai quartet. So no idea about Kazuma.
He doesn't really deal a huge amount of damage. Rather than glasscannon, he'd be a glass with cheap tricks.
i agree that Cale from Trash of the Counts Family fits (though he's an unreliable narrator). he's surrounded by OP people but whenever he uses his own power he's weak as hell.