Absorption Line requires the usage of the Holy element to be cut, and of course something sharp, so all in all only Kiba and Xenovia can cut through it. Also, he didn't think it was a big deal and wanted to see where it'd lead to.
Well, is the Dragon Slayer not a Holy Sword by itself? - anyways, seems to be some quite powerful ability then, imagine stealing the power of Vali... especially when he is alone and no one with a holy sword in the Vincinity...
They have no issues fighting, both enjoy fighting (Bikou and Vali), however they've other missions which they're equally excited about (since it involves more fighting), so they're extracted or simply go (depending on which scene you're referring to).
Also, the Devils side have very powerful figures (such as Sirzechs) and in some events they were hosting Norse gods (such as Odin).
I Get that they have no issues fighting, i just say that if someone is that powerful, why isn't he already conquering half of hell or heaven?
Sirzechs might be a bit more Powerful, but the Episode with kokabiel told us that he would probably have no chance against Vali.
Kokabiel said that the boosted shot, Rias hit him with, was on the level of an ultimate-class devil, just a tiny bit short of a satan. Which is exactly what Sirzechs is, no? Which means, that one shot, that Kokabiel simply took head on, wasn't far from the strengh of soneone of Sirzechs Rank.
So if Kakabiel, who didn't have even the slightest chance against Vali, could take someone like Sirzechs head on (what he tried to achieve when threatening Kuroh Academy) it s not very believable that the likes of Vali hat any issue with destroying Sirzechs.
As i Mentioned, this Bikou-Guy didn't seemed not concerned at all to fight an ultimate class devil (The Dragon) plus our Protagonist in overboost at the same time. - Such People can do what they want, go where they want and take what they want.
And this wasn't even taking into account Arthur. Who must be _very_ dangerous for devils as wielder of two holy swords now. - One which can Cut through Space... Considering all this - they could simply have gone to the Party, slaughtered half the population and still escape by cutting a hole in space, if the devils should be able to summon anyone who really poses a threat.
So i guess if the king of hell isn't even in the top 10 of the stongest beings out there, those top 10 seem to be rather tame in their demeanor.
Power corrupts, so absolute power corrupts absolutely... so you would think...
But maybe i'm just missing some great Masterplan that has not been revealed yet. - Still interesting to find out what further Abilities Koneko might have (think about that poisonous Mist, her sister used against Rias) and if Akeno finally accepted her heritage. The last rating gae did not tell us anything about her progress.
