Quote Originally Posted by DeathscytheVII
Plus, I think Hitsugaya stated that a lieutenant class shinigami should be as strong as an Adjuchas, and since Rukia is described as being as strong as a seated officer (BEFORE the events of Ep 1 started, comment by Renji i think), that is sufficient explanation for me on why she can 1 hit KO a menos.
This keeps being stated but a seated officer goes down a LOT farther then Lieutenant. Seats just generally mean you can release your sword in the first place.

The fact is Rukia is also introduced in the beginning after whenever Renji last saw her and virtually crapped herself at the sight of a Menos and was amazed Ichigo could so much as wound the thing forget killing it. There is not even the most remote question she would have Zero chance against a Gillian before the first episode.

Also note I don't mind she can kill a Gillian that was never the problem. Its killing them effortlessly in 1 swing without so much as releasing her sword or using any spells that seems totally unreasonable to me at least.