Karthus needs an execute indicator.

Eve Indikator doesn't indicate that ult will kill, it indicates that the Bonus damage will occur. This is even Said in the Champion Spotlight.

Would be okay to show an indicator that the damage would be enough to kill. But his ultimate isn't technically am Execution, and it's damage is honestly really high.

Eve ult doesn't tell you if it's enough to kill just if it's going to deal the execution portion of damage

Well I don't feel this would affect Karthus that much. Karthus's ult is always used to try and get at least one kill, sure, but you're still damaging all 5 champions and even if one pops or you're most likely gonna shove the others out of lane due to it's massive damage so getting a kill really doesn't matter too much.

I would actually really like this. Sure it isn't an execute, but what better way to truly make him the deathsinger than to make it one?

It's not an execute so it doesn't deserve an indicator. Besides, it won't be accurate at all because ulting takes 5 seconds and in that time, a lot of things can happen.