Food for thought: Lina Inverse didn’t take credit for calling Gaav, but she did with Hellmaster even though the Lord of Nightmares actually did. With Gaav, she merely weakened him. Hellmaster dealt the final blow. So, she doesn’t take credit for it. However, she didn’t really…
Then you can say the same thing about Gaav since she used ragna blade with the intention of killing him. She just didn’t deal the final blow.
No. She used Ragna Blade with the intention of killing him, however, the spell did not work like she intended/hoped it would, and after the spell took full effect Gaav was still alive. Her attempt was unsuccessful.
The spell she used to kill Fibrizzo, however, worked exactly has intended, and after it took full effect - that is, not just after L-sama came, but after she left, since the spell worked as a temporary summoning, not having L-sama stay, but having her come, do this one thing she was called for, and go, - so, after the spell took full effect, Fibrizzo was, as Lina intended, dead. Lina herself being alive was not an expected effect, but we are not discussing Lina having managed to stay alive, we are discussing Lina having killed Fibrizzo.
Now, had Lina’s plan gone awry in any way, this would have been different. If she had intended for L-sama to kill Fibrizzo for some other reason, or generally to act differently, and had the situation just resolved in her favor coincidentally/unexpectedly, or had she just not intended tos summon L-sama with the spell at all, then yes, it wouldn’t have counted.
However, in the anime (which is what I am talking about sorry if unclear) L-sama explicitly says that Lina intended to summon her and knew she would die in the process. She also says Lina did it for Gourry but I’m going to ignore this part now and forever sorry while I go puke.
Ahem. So, in anime canon, the key part to Lina’s claims to credit for Fibrizzo’s death is EVERYTHING WORKING AS SHE INTENDED.
As a parallel example which will hopefully illustrate my thinking here, let’s imagine that there is a king. And his son hires an assassin to murder him. And the king is successfully assassinated, and his son inherits the throne.
Was it the assassin that killed the king? Yes, absolutely.
Was it the prince that killed the king? Also yes.
If the plan was found out and there was a trial, they would be both guilty of king’s death. Not just the assassin, but also the prince. Because it was his plan and therefore his doing.
As a conclusion: I know nothing about the novels, but in the anime continuity, Lina absolutely totally killed Fibrizzo.
Yet, Lord of Nightmares didn’t attack Hellmaster at first. She made it clear to him she is the boss and only attacked after he did. She also granted Gourry’s his desire, and partially Hellmaster’s. While Lina summoned LON, she certainly wasn’t the one making decisions including who lives or dies. Therefore, either Lina is taking undue credit in certain respects which isn’t her normal behavior or she identifies as LON as well.