The title pretty much says what this is gonna be about. So, I'm a big fan of Leona. I like really tanky characters. Which is why I love being ahead on Cho'Tank as (in a game earlier today) Xerath's full combo took 20% of my HP and I walked away, last hit a few minions and I'm back on full health. Anyway, tanks and initiators are my thing. I make plays for my team. If I see a chance, I just go straight in there. Leona is one of those champions that can work out really well when you do that. See someone out of position? With a Leona on their ass, they are pretty much dead.

That being said, I HATE Leona in the bot lane with a passion. I despise aggressive supports. I refuse to pick them, no matter how much my team beg me for it, I just pick something else. I can't combo on Ali for sh*t, Blitz is useless. You have a grab, a knockup and a silence? Lulu says hi, she has slow, polymorph, shield, haste, knockup, aoe slow, and HP increase, oh, and a small damage steroid. Leona falls upon the same problem as Blitz there. Being a champion not initially designed for the support role, she doesn't really bring much to the team.

So, first up, let's look at Leona's kit. I'll simplify it a bit in explanation though:

P: Leona's abilities leave a mark on the enemy. Autoattacks and abilties from other champions on Leona's team detonate the mark, dealing bonus magic damage, the bonus damage is attributed to the person who detonated it. From this, we can tell she is supposed to be used around other people. She works best as an all-in champion where once she goes in, her team follow up.

Q: Stuns the target. Resets the autoattack timer. It's simple CC that's easy to land. You go in, then you use. Meant to be used in her combo to further lock someone up.

W: Grants Leona bonus armor and magic resist for 4 seconds. If she deals damage to anything when the shield explodes after 4 seconds, the armor and magic resist bonus is extended by 2 seconds. So basically, it's there to make you that bit tankier in the fray. You should hit someone with it to maximise its usefulness.

E: Skillshot that passes through targets. Enemy champions are immobilised for a short duration. Leona dashes to the furthest champion hit, putting her right in front of their (about to be dead) face. This is your main initiation tool. That's all there really is to say about it.

R: Skillshot aoe that deals damage after a short delay. Targets hit in the middle are stunned, while those on the outside of the aoe are slowed. In short, you can use this to make a easier shot for E, use it to cut off escapes, add extra CC elsewhere in a fight. Maybe you are right on top of the enemy ADC but their Katarina got behind you, so you drop it to cancel her ult, for example.

From this, we can conclude that Leona is an initiator and a tank, bringing a hell of a lot of CC to the team, while also potentially providing a lot of damage too. I can understand why she is played as support. Not long after I first started playing (about a month), a friend of mine (at the time, Diamond Elo in S2, EUW) told me that Leona was used as a support because she was useless everywhere else. At the time, I just took his word for it. He was diamond having played from beta, and I was new to the game. He knew what he was talking about and I was in no position to even try to refute him. Now having been a player for 14 months, I am in a position to claim otherwise. Here is why I think Leona is considered to be only useful in support:

  1. Her passive can only proc from damage from her allies. Meaning it is wasted in a solo lane. My solution to this will be given later.
  2. Other people do her job better in other roles.
  3. Leona is capable of scaling well from assists, like most tanks.
  4. Her lockdown can set up easy kills for an ADC.

These aren't horrible points. I disagree about her passive, I also disagree about other champions doing better in other roles, I think her potential in another playstyle for top lane has been left undiscovered. I agree that she can scale from assists. Finally, you don't have to be in the support role to set up kills for your ADC. Sure, you can do it more, but that's not nescessarily a good thing. Now, here is why I think Leona is wasted in the bottom lane:

  1. Supports don't get much gold at all. Once mid game hits, you won't have many items and won't be all that tanky.
  2. Following on from the previous point, you can't go in to initiate a fight any more, as even if you lock someone down, you will die for it because you aren't tanky enough to take all the focus because you can't afford big enough tank items, because you were support. Can't do your job as initiator? You better have something like Malphite top/jungle, because you certainly can't do it.
  3. Leona's rank 5 W gives 70 armor and magic resist, making health really cost effective on her. Most health items, however are either expensive to combine (from lots of compnent parts, take Aegis for example) or require few but expensive component parts, which a support is unlikely to be able to afford (Sunfire Cape, for example). Some items, like Randuins and Warmogs are a combination of both these things.
  4. Leona can potentially have fairly low cooldowns, especially with CDR. As support, she goes through one cycle of skills and then dies. A full tank Leona with gold, however, can go through two, or even three cycles of skills. More CC = more lockdown = more peel/containment = more won teamfights = more wins.
  5. Leona's passive can still be used effectively, even outside of support. As whether you were in support or not, when teamfights happen, you will be there. A farmed/fed Leona will be more useful than a squishy Leona.
  6. In 1v1 scenarios in lane, Leona has massive trade potential. Being on almost the same level as Renekton or Wukong. She can put out lots of damage and the enemy laner can do nothing about it.

So, where does Leona fit in? I believe she is most useful in the top lane. Specifically, as an anti-snowball counterpick lane. Very, very few people buy QSS or bring Cleanse into the game. Cleanse is considered an ADC only summoner, even though it cna potentially be useful in any lane. Here is the kind of scenario you would play Leona top lane:

"Oh no, they have Darius top? If Darius gets fed he will roll our entire team and pentadunk us!"

"Oh no, they have Nasus top? He hyperscales, we must not let him reach that point!"

"Oh no, they have Akali top? Don't let her snowball!"

Notice the pattern? It's a denial pick. None of those would specifically bring Cleanse to lane, so your lockdown will be very effective. What you do, which is what uses her passive is to have your jungler (an aggressive one or one with lots of CC like Maokai, Nocturne, Udyr) camp the lane. Your passive isn't being wasted because your jungler is the one getting that bonus damage out. Leona's base stats are just fine, so she won't have troubles last hitting or farming in that top lane. Her combo remains unchanged. W ---> E ---> autoattack ---> Q combo will do plenty of damage and lock the enemy laner long enough for your jungler to come in and further ruin their day. That enemy laner should either die or be forced out of lane. You will therefore get kills/assists and more cs, while denying them from pushing the lane to the tower while they are busy coming back to lane. Rinse and repeat. That scary top laner can't get to that scary point any more. If you have a snowbally, carry jungler you can give the kills to them and still snowball top and deny that enemy laner what they so desperately need. Even if you only get assists, that's enough. You're getting plenty of CS being in a solo lane and will get those big items a support would not be able to get usualy.

Then mid game comes. Now you can do your job! You have Sunfire/Benshee's or any other item if your choice, while your enemy top laner has been denied that they will be insignificant. Heck, you may have even forced them into buying QSS. You can initiate teamfights and not die. You can help snowball the game. You can now bring more to your team, while also having a support in your teamcomp that brings more utility to the team than Leona does. You can have both!

Another thing you could bring to lane is Teleport. If something goes down elsewhere in the map, you can teleport in and Leona lockdown will end in a kill with a co-ordinated team. That will allow you to snowball your and another lane. Possibly even forcing an early surrender.

I don't really have much else to say. LCS NA started long ago, and I've made my point. I just find it sad when a champion is relegated to a single role, then gets stuck there because people can't get past the point that some players do still theorycraft, and do want to try new things, but "NO! LEONA IS SUPPORT U NOOB!" Those noobs can't even think for themselves....

TL;DR: Leona counters practically every top. Not kit-wise, but playstyle wise, and she is therefore more useful there than support, which limits her potential capabilites.