Whenever I talked to other players about why some ultimate abilities have execute indicators and why some didn't, I always got an answer along the lines of "The certainty of knowing when to kill would be too strong" or "Execute indicators don't play nice with resistances as it can change how much damage is actually needed to kill". While I can certainly see the case with the former, the latter I find interesting now since Akshan's ultimate does normal AD damage, but has an indicator that accurately informs you when you can kill. Formerly, these kill indicators were reserved for champions that could easily know beyond a shadow of a doubt that their ability would kill. Through easily understood kill thresholds and true damage. Those abilities of course being Urgot's Fear Beyond Death, Cho'gath's Feast, and Pyke's Death from Below. But with Akshan on the horizon that's no longer the case and it makes me wonder what are the actual reasons for champions like Darius or Garen to not have execute indicators? At the very least Garen's ult shares a lot of parallels with the other execute ultimates but doesn't have an indicator. Previously I could blame the fact that it does missing health damage but it seems that dynamic damage is not as big of a deal as I thought.
So what exactly do you think gives any one champion the right to have an execute indicator? Kalista for example. She is the only champion to have a sub 100% AD ratio on her auto attacks (it's 90% currently, if you were curious). That's okay though, because this is to make up for Rend having a 60% AD ratio, so all in all technically Kalista has a 150% AD ratio on her auto attacks, conditional to her successfully casting Rend. The problem comes in though, with that Rend has a pretty lengthy cooldown (14 - 8 seconds based on rank). The cooldown of Rend resets only if Kalista gets a kill with Rend, it doesn't have to be a champion but it has to be something. Yet, on top of dealing with a shorter than usual range and her very unique passive, when exactly does Rend kill is a mystery to Kalista. The victim's guess is just as good as Kalista's in this case. She can count the spears visually, even left click her target to see the exact number of stacks a target has but because the damage is primarily an AD ratio it's ultimately still guess work. And the price for guessing wrong is a 60% penalty to your auto attacks, which is really bad on an ADC.
Akshan on the other hand, has a passive that grants him extra gold and revives teammates on kill. That's pretty good but, there's no real penalty for messing it up that I can see. If Urgot's ult doesn't kill he basically doesn't have an ult, if Cho can't eat bad guys then he doesn't get to be tanky, and if Pyke can't execute enemy champions then the team is stuck with a support who isn't tanky, has janky delayed CC, and the ability suicidally flip someone over his shoulder every 8 seconds.