Increase your Tenacity and Slow Resistance for each summoner spell on cooldown. Immediately after casting a Summoner Spell, gain a larger burst of Tenacity and Slow Resistance for a moderate duration.
Offense
+5 AD or 9 AP
Flex
+5 AD or 9 AP
Defense
+6 Armor or 8 MR (match-up)
WhyElectrocute
Akali loves burst damage and she can quite easily proc Electrocute with a [Q]->Auto->[E].
WhySudden Impact
Akali can make use of both the Magic Penetration and Lethality of Sudden Impact, while nearly always having the proc up with [W] and [R] casts.
WhyEyeball Collection
Akali loves to kill and snowball. Eyeball Collect is perfect for bloody lanes/games where you're looking to run away with a lead.
WhyUltimate Hunter
Akali's new [R] has insane kill potential thanks to its high damage, but that comes at the cost of a long cooldown. Ultimate Hunter helps give you more opportunities to kill and carry any game.
WhyBone Plating
Bone Plating's early game damage mitigation help you through the early laning phase so that when you hit 6 you're not too far behind and can find kill pressure.
WhyUnflinching
The hardest counter to Akali is CCing her while she is out of [W] invisibility. Unflinching helps patch up some of that weakness.