Nov 3rd 2008 1:07AM first of all, Sargeras is strong, yeah but if you read the bocks you'll notice that the older gods plot to destroy sargeras and take over the burning legion. They where 100% sure that they could take on Sargeras without any problems, so no Sargeras is NOT the strongest character.
And no it's not deathwing, he is simply to weak from the beginning to even mention.
No it is not medivh, the only spellcaster that deathwing feared was medivh, yeah true but he did only fear and deathwing whould prb be able to take on Medivh if he really wanted. (Sargeras possesed Medivh even and that could be the reason for deathwing's fear of medivh)
Also the titans required more then just a handfull of titans to take on the older gods, 5 older gods against a huge amount of titans, fair? no. 1 older god against 1 random titan and the titan whould have his ass whooped no questions about it. Altho if it whould have been one of the leaders of the pantheon it's still hard to say because we really dont know anything about them, still the titans required numbers which the older gods did not.
So in the end it's the older gods because simply as that the titans could not take down the older gods first of all without a real fight and secondly not without their huge amount.
Also, Arthas is not an option, Kil'jaeden created him and I'm quite sure that if arthas whould come to the twisting nether he whould been defeated, since Kil'jaeden cant enter azeroth and when he did last time he got weakened. Yeah he sent illidan, but that is because he simply cant go there and do it himself.
The thing about Elune is tricky aswell, she's a godess yeah and she stopped archimonde from killing tyrande with a shield which he couldent pierce and yeah she gives all the priestess their powers. What else? Nothing, we dont know anything else about her so we cant really take her as accounted.
Now, the mightiest beings that's still roaming the kingdoms of azeroth: Arthas, the aspects, every damn faction leader. That's it, everything Arthas has to mess with is the aspects and the aspects 4on1 whould prb kick his ass, but 1 aspect against 1 merged lich king who controlls hundred of thousands undead and becomes stronger each and every day. I whould throw my vote on arthas, simply because the aspects whould never be able to get to him first of all, secondly he's badass, and thirdly his mount was one of malygos prime mates, Sindragosa he ressed one of the mightiest dragons on azeroth to have her as a mount, same with sapphiron. What does that tell you? that yeah sure we dont know if he whould pwn the aspects, but 1on1 against for example malygos or the red dragon queen he whould win. Against Nozdormu no change in hell. (the titans also knew that since he controll time he whould be the most powerfull one) Controll time and being a BIG fucking lizard > ress humans into ghouls.