"Without plot devices, Batman hardly defeats anyone."
Your getting my point then, this isent Thanos with a plot device. Its Thanos on its own power.
"It takes a lot to wield the IG. Thanos's (niece?) couldn't handle it."
Thats why Thanos stated when Nebula was figthing the abstracts that even a fool with the IG would be invencible?
In true she did the exact same thing Thanos did. Fought the cosmics and abstracts all at once, defeated them and imprisioned them. And the she lost the IG like Thanos did.