To the point Riot cannot do anything to progress it and they can only add scenes of what they are doing after their story ends.
Like Darius settling down and having a family or Azir just having a friendly chat with Sivir after he rebuilt Shurima
How would you like it to go?
It doesn't mean they have to die in the end.
veigar meet ben shapiro
Xerath going in the celestial realm, leaving Shurima to Azir.
It would be nice if his lore started before that.
To have a good story and development before they are finished from being in the spotlight. And I would very much like if some characters die.
Aatrox succeeds at his goal, thus ending all champion lores permanently. Saves the effort of writing 150+ pieces.
finds her tribe again, leads the people of Shurima to democracy, helps defeat Xerath, and spends her days stoneweaving and adventuring.
I'd want them to go out in a blaze of glory, and maybe get martyred, so the idea of them never dies and maybe a cult about them forms
conquers all major factions(starting with Noxus), pulls down he gods of targon, breaks whatever Shurima 
is building, razes Piltover/Zaun, burns Ionia, drives out the Void. A world of undeath is born. The remaining heroes 
etc put aside their differences and unite against him. They defeat him finally, and banish his spirit permanently from Runeterra using the runes held by .
The world is now cleansed of Darkin, Void creatures, and the power of Targon. A new age of peace begins.
Ahri finds someone who makes helps her forgive herself for her past actions and settles down.
a perfect ending for him is death. After he restore the blessed isle.
Brand accidentally falls into the bathtub
"Permanently end?"
There's no permanent end (outside of death), friend, there's just a point where the storyteller stops talking. There are very few champions that could even have a true "ending" wherein their story is complete and they have nothing else to do or anywhere else to go.
Example1: Even if Shurima is rebuilt and the issue of Emperor/Empress decided, there will be political issues to deal with. The Void will always be a problem. The potential threat of the Darkin returning. Noxus remains an imperial powerhouse. Shurima may very well decide to expand east, into Kumungu (or whatever that are of jungle is called now)
Example2: Let's say Nami gets the moonstone and returns home. Would the Marai tribe truly feel like home anymore? Now that she's seen so much of the surface world, seen so much of not just the world but the very real threat that the Void beneath her people poses to all of it? Could she really just go back under water and live her life as it was?
Example3: Even if the Freljord units under Ashe, Sejuani joins her as her military commander, and Lissandra sees the error of her ways and joins with them both (incredibly unlikely), that would mean that the Freljord just became an international power. They would have to deal with Noxus and Demacia (heck, the two might see a united Freljord of this scale as a legitimate enough threat to necessitate it). The demigods of the Freljord are still a thing.
etc etc
I honestly don't know. It's kind of hard to imagine this kind of stuff when you don't know every information about a champion... As a Syndra main, I honestly couldn't tell you because I lack knowledge about her powers and what they can do exactly (we know what she can do when she's angry and bitter, but we don't know if things would be different if she were in a different state a mind), and depending on the nature of her powers I could imagine different ends to her story. Now, in the current state of things... I may have an idea? Not sure I would like it, but still. I can picture her going against a very, very powerful enemy (like, real threat you know, not just a powerful human), and in order to defeat said-enemy, she'd have to use all her powers, and more. She'd have to unleash all her destructive potential, and go beyond what she has, but it would ultimately be too much for her body to handle, and she would die. Yeah, I'm not crazy about that idea but it would be cool. I just want to see Syndra unlocking her full potential at some point. :')
The work was inescapable. Together or apart, Zed and Shen would chase the clues he had left. They would follow them back to the Blossom Festival. Back to Jyom Pass. And when they became desperate, then they would have to work together again.
It would be like it had been when they were young. They would huddle together in awe and fear.
Only then would the great Khada Jhin reveal himself…
And his true masterpiece would begin.
There is only one end. And it will be beautiful. It will be... Perfect.
For 
I'd like for her to finally fall in love and maybe someone like Evelynn to could rip it away from her leading her to loneliness forever as a reminder of what's she's done to other people's families
After he was freed from the curse of his sword, Aatrox has a tea party with Zoe and Pantheon so they could finally settle their differences and forget the past.
Obviously it'll never actually happen but I just thought the idea was funny.
and 
settling their differences and rebuilding the solari and lunari as one tribe
I would like 
to finally beat the entity that is spawning the void, because then the Targonians wouldn't have to keep him enslaved.
Skaarl dies
Tbh Azir's arc wouldn't end after probably beating Xerath and rebuilding Shurima. He has Noxus to worry about, the Void, Shadow Isles etc. Nation leaders in general won't have their lore ended unless they die, and please, PLEASE don't kill Azir.
The 
are alone. The hunts are all over. Everything that ever was or ever could be is dead and alone, except for them.
There's only one thing left to do.
The two eternal companions face each other.
Lamb aims her final arrow.
Wolf readies to charge.
"I love you." Wolf whispers. "I know." Lamb replies.
He charges, she shoots.
And we cut to black.
