A Thought on what makes a well designed Passive

In my opinion, a well designed passive is one that adds depth to that play style, or accentuates why you want to use that champion in a particular way. For example, does anyone remember when Xerath and Lux's passives were put into question? Why would these long range ability centered champions have passives that effectively require them to give up half their usual range to use and all that stuff? Well, consider the alternative, where Xerath can spam waaaaay more abilities than he currently could or Lux having the firepower of her passive added on top of her individual abilities, all without ever needing to walk within 1000 units of their respective targets. These champs would be horribly obnoxious to work around as their kits promote killing you from way farther than most champs can possibly reach and otherwise limiting player interaction and its effects, something I'd consider terrible in a multiplayer game. By tying valuable power to these champs onto a play style that forces them into a much more manageable range for their opponents, the alternative scenario I described becomes far less prominent, and (in this case) it greatly increases player interaction to a kit that puts its strengths in limiting player interaction. This is depth. These are admittedly simple kits on the surface, but just that interaction between their passives and the rest of their kits adds that much more depth to their play styles and thus to them as champions.

The other kind of a well designed passive can be seen in champions like Ashe. Her passive is not one that necessarily adds depth; whether she has her passive or not, she probably would be played similarly - if not exactly the same - either way. However, it does accentuate her as a champion. Ashe is the ADC you use when you want to grant the team that much more utility. You don't pick Ashe for raw punching power like Vayne's tank shredding or Lucian's burst, you choose her because of the near unmatched amount of CC she can offer to the team compared to other ADCs. Giving her passive the slow it has now helps emphasize that she is the ADC you use to lock down targets.

I wanted to point these qualities out because sometimes, it seems like there are champions that just seem to miss this mark with their passives. Sometimes it's just a matter of that passive just not fitting with the rest of the kit; we can see this in Amumu's Passive. Cursed Touch would add depth to his kit if Amumu's strengths were in ranged damage towards squishy characters. As an AOE Dive Tank however, or at best an AP Bruiser, whose abilities are all close ranged, its a passive that can be too easily used on targets that he would be hitting anyway, not giving any depth to his kit nor accentuating why you pick Amumu. Other times its just a passive that happens to be there, adding unnecessary power that neither grants depth nor accentuates specific traits of a champion, such as the Auto Attack part of Yorick's Passive. An extra 5% damage on all auto attacks may at best be an odd gimmick in ability focused champions and at worst is truly extraneous power in innate auto attackers.

What are your opinions on a well designed passive, and what champions do you think don't have a well designed passive, either by my or your standards?