Across 1,038 ranked games on patch 16.21 in Master and above, Pantheon mains win 53.2% of their games in the top lane.
Their most common build appears in 29.0% of those games and wins 55.5% of its 301 games.
It starts 
Doran's Blade and 
Health Potion, completes 
Bastionbreaker, 
Voltaic Cyclosword and 
Lord Dominik's Regards in that order, and takes 
Boots.
Three other builds are played often enough in the top lane to be measured on their own.
In the top lane, Pantheon mains fare best against 
Fiora (won 84.6% of 13 games), 
Urgot (won 78.6% of 14 games) and 
Jax (won 75.0% of 12 games).
Their hardest matchups, the champions that counter Pantheon, are 
Aatrox (won 33.3% of 15 games), 
Sion (won 38.1% of 21 games) and 
Malphite (won 41.2% of 17 games).