Against pantheon, Watch out for a potential Flash engage by Pantheon. In team fights, don’t stand too far forward in case he tries to make a play.

Ward your flanks! Pantheon may try to attack you from the side and get on to your carries when his Ultimate R is on cooldown. 

Good times to fight is when Pantheon is split pushing. Forcing a fight when he is on the opposite side of the map could be a good idea as it will take him some time to get into the fight even with his Ultimate R.  Against pantheon, In team fights, don't stay too far ahead in case he tries to make a game. Watch your flanks! Pantheon can try to attack you on the side and go to your carts when his Ultimate R is on cooldown. Good time to fight is when Pantheon is divided push. Force a fight when he is on the opposite side of the map could be a good idea because it will take him time to get into the fight even with his Ultimate R.