Pantheon vs Sion Top Matchup
Pantheon Top wins 48.1% of 722 Low Elo games against Sion Top, -0.4 points vs expected, 2-patch window 26.19-26.20.
Researched on LoL patch 26.20. Tips are written to hold at any rank; stats come from Low Elo ranked games up to patch 26.20.
How to play as Pantheon
Plan the wave around Sion's Glory in Death(P) instead of assuming a kill denies his farm; he can still attack minions during the passive.
If Sion becomes too durable to threaten in a direct duel, shift to roams and teamfights rather than repeatedly forcing solo kills.
Sion's Glory in Death(P) lets him keep attacking after Pantheon kills him, so the takedown may not deny Sion the wave.
Sources
These notes come from r/PantheonMains, checked against the champions' abilities.