Ok disregarding veigar and all, I feel she would be a good candidate for best scaling. Passive is like GA better than karthus on a way cause she won't die at the end if she lives. Her wall is super useful and her AS slow is great if someone else also has frozen heart.
IceKingChernobog3 votesshe would if she didnt use 3 spells that use up 80% of her mana each time
Too Ton1 voteswell late game you should have roa and maybe tear if you sacrifice deathcap maybe idk
ImpendingDeath3 votesIt doesn't matter how well Anivia scales when she is constantly OOM and one of the least mobile champions in the game. She needs absurd scaling to be even slightly relevant in the current meta, though she fails even at that.
Pryotra1 votes^ someone who knows nothing on mana mangement.
Serisously, the answer here is yes, she is one of if not the best scaling AP champion in the game. With that in mind, her earlygame did at one point include a very serious managate. They reduced it significantly, but the managate does exist early on.
She actually handles being immobile fairly well, with pretty good clear post 6 and a reletively safe lane due to all her CC + wall. That, and she does a pretty slick combo early for incredible early damage, even if it is costly with mana. If you land her Q, which is a difficult skillshot to land nowadays, you follow up with E for about 60% of their HP bar. A pretty fair trade, considering that she can't spam it due to mana constraints.
If you can last hit well, Anivia is a fair choice to master for midlane.
ScurvyNave1 votesIf you can last hit well, Anivia is a fair choice to master for midlane.
Wouldn't the past nerfs to mana regeneration in general and the nerf to 
make Anivia even more mana hungry than ever.
If she isn't able to use her wall (which half of the league champs can dash through or over) and her spells to deal the damage and control zones like she used to you might as well just pick Karthus instead or some other AoE mid laner.
I am a great fan of Anviva but in Season 5 and this current meta Riot might as well have clipped her wings.
Pryotra1 votesOh, Anivia has a mana bar, and she always has. That said, I usually bought a tear on her early anyways, as that gave Anivia everything she could want. If you manage your mana right, Anivia can win lane without the wall, especially against squishy assassins with no CC and her passive. If you need more help than tear, I recommend Morellonomicon, as it also applies GW in her ult. I've used her recently, and she feels about the same as always, so nothing really changed for her this season.
Honestly, Anivia still does OK. Yeah, the sharp increase in mobility has hurt her wall game, but she still teamfights almost the same, as the wall can force some knee-jerk dashes and sometimes even catch people out while their dashes are down. Her damage actually still hits hard in teamfights thanks to her icicle being targeted (thank god for Point-Click), and her stun is really more of something you follow up on other peoples CC with until you are good with it. With multiple 100% AP ratios in her kit, she is still capable of holding her own.
That said, She is an AoE midlaner. And like lot of AoE immobile midlaners, she has the potential to work wonders. You just really gotta learn how to use her. Anivia is one of the few old champs that is a pain in the butt to learn, and you should expect to die and die often. However, once learned you will find that there is a reason that the only thing they have really changed on her is her mana costs (yeah, they used to be higher).
GLWuffie2 votesAnivia is an insanely good champion when played correctly. The biggest downsides are the current top complaints by everyone right now: mana regen and mobility. Anivia is REALLY slow in movement and almost everything she does (even attacking/casting abilities/Q speed). Top this with huge mana costs for her poke/combo, and she gets to be an unpopular pick. As more and more champions become more mobile, it becomes really hard to hit for decent damage pre-6.
Another thing I almost forgot is that she also has consistently low base health (most likely due to her passive, she has the lowest starting and second lowest base health at level 18).
If you can find a good build (and manage the mana), you should be able to go GREAT with her.
Default End Build: 
Rush the ROA, get boots, Morello's can help with some mana issues (Athene's for a tad help against annoying AP mids), Deathcap for a huge spike in burst, Void Staff to keep your burst high amonst beefier champs, and Hourglass to give you late game breather as well as another huge spike in damage.
Start E, Q, W, then max (R when you can) E -> Q -> W. Hitting E after a Q or R results in devastating damage and poke. I picked E as the first spell because it helps with Anivia's slow autoattacking to help last hit until level 2.
As for Spells, I personally like Ignite/Teleport. Ignite is always a very great combo finisher when you go all in (R/E/Q), and teleport can be used for two things:
Hope that helps in regards to if she's great at scaling. (Mid game is her forte, late game she falls of a bit, but can still be a huge game-changer).
~GL
67chrome1 votesIs anivia the best scaling mid?
She's not the best-scaling in any realistic application of the word.
I'd probably go with 
for AoE, 
for single-target, 
for a decent mix.
For AD probably 
, though 
and 
have similar potential.
is also noteworthy for being a terror late-game.
EzraTwitch1 votesIn terms in Pure AP scaling 
remains the king of AP ratios (its something like 5.4 on a single target if you bounce your ult just right)
Skia Asteri1 voteshttp://champion.gg/champion/Anivia/Middle
Compare the win rate vs game length graph on the right of that page with those of the following 'late game' mid laners:
http://champion.gg/champion/Cassiopeia/Middle http://champion.gg/champion/Azir/Middle http://champion.gg/champion/Orianna/Middle
Contrast with:
http://champion.gg/champion/Morgana/Middle http://champion.gg/champion/Leblanc/Middle http://champion.gg/champion/Brand/Middle http://champion.gg/champion/Annie/Middle http://champion.gg/champion/Syndra/Middle
She is an early / mid game champion. Because her base damages (which are pretty high) start falling off once you run out of damaging abilities to level. And 
is good at all points in the game.
BakedLotion1 votesanivia never falls off... She has insane utility along with 200% ap scaling on just her e and q. Her R hurts like an asshole late game also, even more if you buy a liandry.
Drunk Rummate1 votesdepends on your definition of scaling. in terms of raw damage she does a lot yeah, but she has huge weaknesses as a result of that.