Well, if our T5's are roughly comparable then the characters I mentioned should be a decent match for him. However that doesn't always equate to firearms and the like, as we both know, they can be a serious challenge even for otherwise powerful characters. I'll wait for you to check them out.
The T5 thing is a link btw (I've got a tier system I use since it's at least
a little less vague and doesn't use references to characters as its base line. Regardless...hmmm.
Yeah, I think Adrian or The Clockwork Man would work just fine as Ananze is rather formidable. They would each be challenging in a different way. Adrian would be harder to fight because he's difficult to detect. He doesn't do enough blunt force damage to crush or crack Ananze's natural armor, but his weapons plus his physical strength are clearly strong enough to pierce it so he's got that going for him. Plus Ananze likely wouldn't be able to hide from the vampire (though the vampire wouldn't be able to drink Ananze's blood due to it being more acidic than normal blood by a wide margin)
Reason being, daedri inject their prey with their acidic "venom," before eating it...so they tend to end up ingesting that same acid, so they've become immune to it. Since their body breaks down the food that acid ends up in their blood, making it caustic, though far less so than the undiluted stuff.
The Clockwork Man on the other hand would have to be worn down by acid first, and then likely have his inner workings mucked up with webbing. I can think of some clever ways that Ananze could deal with him, but it'd still put him on his back foot in a way.
It's ultimately your choice, either works, but I think The Clockwork Man would be more interesting than two assassins, or rather one ambush predator and one assassin, fighting eachother.
EDIT: Should probably add that acidic blood bit to the CS. It really only occurred to me as a logical outcome just now.