TLDR The short version is:

The goal of the build is to hard harass with q auto level 1, all in at level 3 (weave autos so you dont lose damage) and during team fights dive the back line, use shroud for cover. Your goal is not to burst down enemies in team fights its to sit in the backline and cause chaos, get kills where you can and stay alive.



Tank Akali — The Backline Haunter
Introduction
This build turns Akali into something the enemy backline has never practiced against: a tank they can't kill, can't see, and can't ignore. You aren't going to burst anyone. You're going to walk into their backline, disappear into Shroud, reappear somewhere else, and make their ADC so paranoid they stop doing their job. The kill is secondary. The fear is the point. A scattered backline that's burning flashes and running sideways is worth more than a single kill every time.

Laning Phase
Level one is pure Q harassment. Every time they step up to CS, Q them and immediately auto to pop the passive mark — don't wait for the Q animation to finish before right-clicking. You're not going for a kill, you're making them scared to walk up. Keep this up and they either take consistent chip damage or they give up CS.
At level 3 you have your full basic kit and it's time to all-in. The combo is Q into immediate auto, then E to stick to them, Q again, and weave an auto anywhere it fits. The key word is weave — don't dump abilities and stand still waiting on energy, slot an auto between every ability you can. It keeps your energy flowing and adds up to a meaningful damage difference by the end of the trade.

Teamfighting — Make Them Scatter
Your goal when a teamfight breaks out is to get into the backline as fast as possible and make their carries feel like they're being hunted. Use R to close distance and land directly on the ADC or whoever is doing the most damage. Hit them, apply your mark, then immediately drop Shroud on top of yourself and them.
This is where the build wins games. You're tanky enough that they can't burst you out, so they have two options: stand and fight an invisible threat they can't target cleanly, or run. Most players run. The moment their ADC starts moving backward instead of shooting, your frontline has already won the fight. Keep cycling in and out of Shroud, re-applying marks, and forcing them to react to you. The kills will come naturally as a byproduct of the chaos — don't throw your positioning chasing a low-health target when you could be keeping three people panicked and out of the fight entirely.
Unending Despair comes online late and quietly keeps your health bar topped off during these prolonged backline stays, letting you linger in the chaos just a little longer than they expect.

The Core Rule
You win this build by being a problem they can't solve quickly. Every second their backline spends looking over their shoulder, flashing away, or burning a key ability into your Shroud is a second they aren't playing the actual teamfight. Be the ghost in their backline, not the assassin going for the highlight reel.