I think if Kled found a world rune he would lock it in a chest and claim it as his property and kill anyone trying come after his rune. He doesnt seem like the type who would use magic.
eat it.
spends the next few years analyzing it, determining where it came from, the ramifications of this rune existing, the benefits and drawbacks of it existing, what she can do with it and how this item could end up changing the face of the world before ultimately locking it away and filling out the necessary paperwork.
"lmao cait look I put this glowy rock in my gauntlets and now I punch fire"
[MONOLOGUING INTENSIFIES]
He wouldn't use it, everything's OK.
Zoe would probably throw it around like a ball
would certainly use it to make the most impressive and devastating performances. Something he'll certainly find to be "beyond perfection", seeing the power they hold.
sell it
Oh boy another dangerous magical artifact to refuse to put down despite its potential world ending implications.
Yorick probably would be SUPER conflicted in using the power of the rune, but ultimately would give into it to try to revert the Shadow Isles back into Blessed Isles.
Ekko would experiment on it. If he decides to combine it with his Zero Drive, he would straight up shatter time permanently. Runeterra would basically turn into Nova Chrysalia from Final Fantasy XIII Lightning Returns.
Exploit its power
Keep it where it is and prevent its use (Defends nature)
Remove it from where it is and prevent its use (ENFORCED Equilibrium)
Attempt to use it to deal with the Curse
... What, did you expect gags?
These shits are like infinity stones right?
One snap of my fingers and Kha'zix will cease to exist
All I'm gonna say is if 
gets a world rune...
Pray.
Use it to break the spell holding him, GG Targon.
Absorbing their power to become an entity powerful enough to face "endgame content" (the Watchers and such).
Help Ryze hiding them.
No need of puny rune-toys, he would destroy them and call it a day. Chance number 2 he corrupts them and uses it to kill every mortal and immortal on Runeterra.
Ignore it and go get a chime in topside jungle
's job would become infinity easier XD
Xerath, even he is currently malevolent I would say, wouldn't use a world rune to destroy Runeterra. His goal is conquering and ruling Runeterra, not pushing it to edge of annihilation. But he would be unstoppable.
Syndra wouldn't use it, perhaps, as she is not interested in power except hers. But runes are corrupting, so she could use it to destroy Ionia.
Lissandra would use it to free the Watchers and doom Runeterra.
Ahri would use.
Orianna wouldn't give a damn.
Evelynn would definitely use, without a doubt.
Zyra, and it'd mean BIG TROUBLE for LITERALLY EVERYONE
He would probably try to hide the- wait...
I'm actually not sure, would he try to expand Noxus over the earth? or would he recognize the danger and help Ryze, Hmmmm.
Oh, Goodbye world,
Goodbye Universe,
Embrace Oblivion normies.
Make the league of Draven a reality.
"This belongs in a museum!"
Elise would either give the rune to Vilemaw or LeBlanc, unless she knew how to use it herself to become a true immortal. Probably Vilemaw, since he's a far more powerful entity.
Vladimir, Veigar and Mordekaiser would use it for its powers. Swain would also use it, but be extremely careful when doing so.
Evelynn and Karthus would use it to cause the most suffering and death possible.
Lissandra and Vel'Koz would give it to the Watchers.
logical course of action: do what did.
bait people with it, as part of a deal.
become sat- oh wait....
new boomerang?
As the undying spirit of vengeance that she is, she would hunt down the Riot Employee, that came up with her Nerf.
[slayer-jinx-wink]
Rammus holding all-powerful World Rune
ok
yea
hold onto it because someone probably lost it.
lock it down because magic.
can you say perma gas?
: Would study it and try to find ways the void could use its power.
: Would hide it away so none could use it.
: Would use it to spread the song of the Shadow Isles and the gift of undeath.
: Would hide it in the most unusual spot so nobody could ever find it.
: Icathia beckons!
Just to list a few
Eat it and absorb its power
ULTRA SUPER MEGA DEATH ROCKET
And those Europeans a few centuries back thought they had it bad
Pretty light show
It's like the Cold War but warm
More research. And we all know science is good for people.
likely would use it irresponsibly, then end up either hurting or killing 
, causing him to snap out of his power hungry state and then.... well f*ck, he'd pretty much become at that point I think, going everywhere to try and prevent the World Runes from falling into other peoples hands.
(kind of the down side of being a champ that has no goal atm. you give him major plot device and that suddenly becomes his whole deal :L )
..... NEVER.... GIVE HIM.... A WORLD RUNE O_O
You KNOW Noxus would be wiped out, possibly end up ruling over Ionia as its protector.
Voice line: Another trinket to be shattered
I could see her using it to help galio be able to be up without her or to just help Demacia when need be.
Give it to the Targonians =O =° =O
and on that note...
TOTALLY HAS INSPIRATION! It's 'creativity and rule bending' and doesn't she kinda know where some runes ARE? And she's TOTALLY EVIL ANYWAY!! Zoe SO has it! I'm pretty sure Aspects would be immune to the runes' effects. She might even keep moving it around via portal just to screw with Ryze.
get taller
... wait... she is already involved!
Drown the world 
i honestly think, 
would be one of the few other people next to ryze who would try to bury or destroy them.
i dont think he would ever be tempted by one. demacia was literally founded in response to the destruction those things caused. whats more is, it wouldnt even be suprising if there was one of them buried right under demacias foundations just to keep it hidden and never to be used.
if ryze could earn his trust despite being a sorcerer, i think they would get along well.
