((Vadriel's biggest weakness is his own pride and overblown sense of revenge...he'll pursue vengeance to his own demise...As well, mere light magic may not be able to do much to him, but REAL power of the Almighty can do the most damage to him out of the things that can hurt him.
Another thing that Vadriel is pretty vulnerable to is water...he's an amazing flier, but he can't swim well, and getting his wings wet bogs him down. I mean, his fire magic can usually bail him out of water-problems, but any hinderance to that can give him trouble.
Also, all he's been faced with so far is mild sorceries...very powerful elemental magic is definitely something he would have to contend with, but think of it..he's from HELL, which is half blazing inferno and half frozen wasteland...he's been exposed to the elements for a long time...it takes heavy guns to take him down...
In addition, he may not be killable in the traditional sense by physical damage, but his body can be ruined, forcing him to leave this plane of existance until he can gather a new body out of shadowmatter. He can remanifest out of any shadow, so a room with NO shadows will stop him from entering once he's been "killed."
And yeah, Vadriel's a beast...the scope of his abilities is pretty damn fierce, so one hit kills are pretty much a given with him...however, unless something pisses him off, he doesn't usually bother with it. If it attacks him, or it's something he bears a grudge against (like humans or angels), he'll take it down with all he's got. However, if whatever it is doesn't try anything with him, he'll either ignore it or merely disable it. So...that's about what you need to know about Vad.))
Vadriel turned to Bathizar and crossed his arms, obviously waiting for a reason to bother with the little human.