Across 803 ranked games on patch 16.21 in Master and above, Akshan mains win 55.5% of their games in the mid lane.
Their most common build appears in 72.1% of those games and wins 56.1% of its 579 games.
It starts 
Doran's Blade and 
Health Potion, completes 
The Collector, 
Infinity Edge, 
Lord Dominik's Regards and 
Rapid Firecannon in that order, and takes 
Berserker's Greaves.
Two other builds are played often enough in the mid lane to be measured on their own.
In the mid lane, Akshan mains fare best against 
Akali (won 77.3% of 22 games), 
Katarina (won 76.9% of 13 games) and 
Sylas (won 69.2% of 13 games).
Their hardest matchups, the champions that counter Akshan, are 
Locke (won 38.5% of 26 games), 
Yone (won 39.3% of 28 games) and 
Ahri (won 42.4% of 33 games).