His fuckin R.
1000 Damage to EVERY PERSON by pressing a lazy R.
You can go 0/10 and you will still be on top.
Why? Because karthus is retard proof, and this is why they cannot balance him.
Solution?
Minimize his R range.
dangopee5 votesThey should make his R an execute Kappa
Girard3 votesI used to be like you, young and naive. And then, one day, I sat down and said, "You know what? I hate myself. I'm going to get rank 7 on Karthus."
Seriously though, he's fair because his ult only does that damage at 40+ minutes consistently assuming people didn't just go full tank or build a maw. There is also a sizable buildup for it so you can prepare to dodge it or shield/heal up. At level 6, his ultimate will do about 180-200 damage on a 3 minute cooldown. It grows to about 320-400 in the mid game and late game it can do 700-1000 depending on how fed you are or what your build consists of.
Karthus is pretty balanced AND a pretty decent skill requiring champion, too.
Astôlfo2 votestfw someone is actually crying about this lmfao
cinomenapplebae1 voteswhat
Oleandervine1 votesKarthus is pretty well balanced. His kit is near perfect, because it was only items, and nothing more, that tipped him into OP when the MYMU rolled out, and even that was quickly fixed with the nerf to the Catalyst.
Handy Sandy 1 votesYeah, it's not like he can be interrupted while casting it or nobody can get a 
or 
Well, only mages should get those. Everyone else is always having 2.5k+ health and is way too tanky to die from karthus's ult. Learn to play around certain champs, like you need to do with every champion.
ZeeWolfZ1 votesYou must've played too many ARAM games buddy.
Oh wait, you did.
Let my whole team build
Handy Sandy 1 votesYou must've played too many ARAM games buddy.
Oh wait, you did.
Let my whole team build
Yeah like that one guy said there's something called magic resist in this game idk if you heard of it, it must be pretty new
redniwediS1 votesI'm not sure if you know this, but there's a damage mitigation mechanic in League called Magic Resist. It helps block a portion of the damage you take from magic damage sources, of which Karthus is one of them. I highly suggest taking some time the next time you're in the shop to find this statistic and invest a bit of gold into it.
Once you have a bit of Magic Resist a 0/10 Karthus should be no trouble for you at all.