Build and Runes
If she activates her Eclipse, it means she’s about to engage.
If possible, Punish her for missing her Zenith blade.
Only the center of her ultimate stuns, and it can easily be dodged with proper reaction.
Leona’s passive allows her team mates to do more damage to anyone she hits with any ability, but she herself can’t activate that passive, so staying away from her team mates when her passive is on you, you’ll recieve less damage.