Mordekaiser is the ultimate manifestation of the Shadow Isles death ladder eco-system. Consequentially he is also probably the supreme authority in the Shadow Isles.
Tristana and Teemo are megabros, relationship overtones only exist because people don't think it's possible.
Karthus trades flesh and unused bodies regularly with Noxus and the Shadow Isles, given their death based economies.
Win Lao has a man respect thing going on with Master Yi.
Champions can compete with summoners in terms of power levels, but due to their different specializations it can go either way. Not a fan of godmode player characters.
The Void born were expunged from Runeterra by the forerunners of the Shadow Isles, who became empowered by the ruinous state of affairs ran by the Void born. As life returned to the world, they downsized as death began to equalize.
The dangerous magical instability of the planet is actually just modern science's limited perceptions of the land mass all the civilizations are on currently. While their continent may become unstable enough to not support life, other continents like Lokfar are far enough they're good to go.
Swain's hobble and cane walking style is really just a force of habit.
Irelia and Leona are megabros.
The League is split between preservers/dominators factions, with one vying for global survival and prosperity and the other seeking world control. While not mutually exclusive, their methods are what make them different.
Some of the ones that came to mind.