Not just on bot, but as any lane. You can build 
, but what do you do until then? Or what do you do if she roams too much and your qss becomes useless? Also, she's so tanky I've seen her 1v1 3 guys one after another with no problem whatsoever.
just dash out with it coming off CD in a couple seconds to do it again.
all easily peel Leona off
As adc: Early game: stay far away (safe distance) from leona. Once she used her E, you can punish her (abilities/AA/...) During mid/late game: Stay backline and be sure to dodge her R. I wouldn't buy qss against her since she has chaincc (you qss one but then you get stunned by her next spell anyway)
Play Volibear support. You can roar or flip her out of her dash if she engages on your ADC, and if she engages on you you can just stat check her.
stop her mid dash lol. janna, thresh, rakan, draven, just a few picks that can do it. but ofc, requires skill.
While leona is on you, the adc is vulnerable. Keep that in mind.
Leona's W is where most of her tankiness comes from. She shields herself, and the shield explodes after 3 seconds. If the explosion hits an enemy, she is shielded for an additional 3 seconds.
if you just stand there and let it explode on you, she'll just be tanky for twice as long while beating you up. Try and avoid the explosion, then turn and kill her with the ring disappears.
Leona can't do shit without her ADC, has no escapes, all-in or die champion. Fortunately, good ADCs are a dying breed, so either they'll pussy out because they got auto'd ONCE, leaving her alone in a 2v1. Use heal RIGHT after she dies or only save it to themselves, or would rather AFK farm instead of taking advantage from a stunned target. Additionally, you can harass Leona in the early game as she can't engage without much hp, and just pay attention for when she's about to use e, if you play it well, you can bait her and make her miss her engage, and her r is there to reach her target or prolong her cc lock down.
TL;DR: Leona engages in hopes that her team would follow, if her team doesn't follow, she becomes a sitting duck awaiting her death.
[slayer-jinx-wink]
A good Leona does that. Generally you wanna have a good support with decent peel who can disengage fights. I've found that (obviously) Morgana is the best counter to her, but you can also viably take something like Janna (played at a distance) or Galio to counter her dive.
Alternatively, you can play a mobile adc like Vayne, Lucian, or Ezreal, as long as you're ready to mash your mobility ability at a moments notice, because once her E is down, it's down for a good second. Use that range to punish her. Either way, It all really comes down to prediction.
Leona thrives on those surprise dives into your backline and pounding on her carries, and her W giving her bonus resistances allows her to be tankier than she really is. True damage champions (Vayne for instance) are good for wittling down her health bar reliably.
If you're feeling really spicy, a good Poppy support will DESTROY a Leona out of place.
ban her
Pick Nautilus. He's the same thing, except better and more reliable. Lol.
Honestly been having a real hard time with her myself. The whole time I have been playing with or against her she has only lost 3 times so far in my games. Only real way I know how to beat her as a adc 
and 
while non adc are maybe with her spell shield and 
ability to just push the opposing adc away when Leona engages and apparently perfect play from everyone else. It seems that way to me at least.
Cause even if you completely shut her and the opposing adc down and dominate the lane. If some other champ is fed she is dangerous and all she really needs is one good engage and its all over. Keep in mind I almost never get to counter pick so I rarely get to use adc solutions to Leona apart from summoners spells and qss. If anyone else has idea's I would appreciate it too.
Fuck Flay.
Basically just about anybody with a displacement renders E engage useless. It is also dodgeable.
As long as you avoid the ult and e she is kiteable and fighters are more then likely going to win a fight against her unless she is building damage and tank.
