Tips from a mainer. Use highly mobile champions and combine it with HARD sustain + tankiness. I main Akali (both assasin and tank) and I also main Yasuo. Having now played tank akali for a large number of games since she became popular, and also having played as my Yasuo VS a few tank akali's I can tell you that three things do tend to screw her over if done right. So again it's Mobility + Tankiness + Sustain.
-The first and most devastating to her is making her blow all 3 of her ults which you can do via 3 techniques. Some examples is use a peel or CC tactic when she dashes to you. Lee sin can dash to a minion as soon as akali dashes allowing her to not only NOT proc her q off you but essentially just blew 1 charge. Lee can THEN ult her back when she comes aback at him the 2nd time. Lux and Morg can also easily Q her while running away to lock her in place as she dashes to you and makes her blow a charge. You can use your savvy dodginess / mobility (via a dash, or a MS boost or whatever) just like above where you actually move away from her AA range after she dashes to you (also preventing her from marking her Q). The reason this matters so much is because you want her to not have any or only 1 ult when you finally decide to go all in against her. And trust me...a lot of them blow their ults trying to proc their silly Q because so many of them have a habit of playing like an assasin AP assassin habits / frame of mind, forgetting that E is their huge source of damage.
-Another thing that hard counters her is hard sustain (like a LOT of it I mean) and then tossing in one of the MR-Sustain items such as Maw, Merc Scimitar, Spirit Visage and so on. This is because you will not explode upon impact to her which allows you to survive her 3 ult crap..while also allowing you to sustain yourself + kite her. Some recommendations for an AD champ would be Yasuo, or Olaf, or Jax. When playing as Yasuo vs her I WAS able to out 1v1 her when I got about 4 items down which were Phantom Dancer + Death Dance + Bloodthirster + Maw. I purposely sought her out when she was alone so that I could turn the tides for my team.
-Obviously tank Akali does a lot more Phy damage than her AP counterpart but please know and rest assured she still primarily does mag damage. As I play tank akali and look at my reports my Mag damage is actually doubling the amount of Phy damage I dealt (despite having maxed E first and having Titanic Hydra or Steraks etc). Now that you know this you can focus more on MR (in case you getting Armor thinking it was helping)
-Another tip which I somewhat stated above is if you get marked by her Q use your mobility to get way out of her range so that she doesn't do the infamous Q-delay combo (which is Q-wait-RAAQAA). Remember, you ESPECIALLY want to maker her blow her ults by using peel or mobility. You can accomplish this with any mobile champion by building tankier items that have some sort of slow or MS boost component (like Randuins, or Merc Scimitar, or Rylais). Remember, she only has 3 charges to her dash so very quickly will she run out of them which allows you to EASILY kite her at that point. She WILL shroud though so definitely have a pink ward.
Tank akali is VERY effective right now I will admit, though not unstoppable. Always remember her biggest counters (do your best to try and incorporate some type of level of tankiness + hard sustain + mobility). Meanwhile provide CC if you can get it from your allies. Oh, and wards! :)
Best,
Seth