It’s more why get hung up on a specific example? Vegeta did far worse and yet he’s a fan favorite, so why is Gajeel so bad?
Also, as I stated it’s more to do with the meme than the specific case someone brought up, everyone can be deserving of redemption, not everyone will agree obviously, but to say that some people don’t deserve it only speaks volumes of your character.
Do not be too eager to deal out death in judgment. Even the very wise can not see all ends.