Give Leona additional in-game dialogue
Just like my Lux one, post up some new lines that Riot could add to Leona.
And as before, stay in character.
Examples!
Encountering 
(like when Aatrox encounters Tryndamere)
"Diana... Why...?"
Taunting 
"The Sun kneels before no one, Emperor!"
Taunting 
"I'll be glad to melt you into a puddle, blackheart!"
Taunting 
"The sun is undying, Karthus! You cannot win!"
Joke near 
"You can't find a more creative use of sunlight?! Y-You fiend!"
Starting a match with 
on her team
"The light is with us, Lux. Let us go forth with its blessing."
, I have always been kind of disappointed that 
has 2 taunts for wu, but not the other way around.
"let us see who has the better shield"
"careful with those spears, you'll poke an eye out"
joke on same team
"you kick them into a well, I will punch them into the sun"
"hey can you bend over and pick that up for me hehehe"