User blog comment:Emptylord/Blogs/Where's the lore going?/@comment-1330314-20130805211935/@comment-1330314-20130805235120

Actually, I always thought Kayle was diving in to finish Morgana off...

Regarding Nasus/Renek, Nasus's own lore states that he was about to slay his brother when Valoran's summoners pulled him through. He may feel guild, but it's more likely he sees no other option but to put down Renekton.

On Leona/Diana, Leona's lore may not specify Diana, but she is nonetheless a paragon of the Solari. Even if she tried to show Diana mercy, Diana herself would still try to kill her, as she's the symbol of everything she vowed to destroy (the Sun and the Solari).