Simlasa
Explorer
I disagree that the 'tonal difference' is always or necessarily present. Those shows have elements of both.X-Files and Supernatural are monster hunting shows.
X-Files most certainly had episodes that were full on horror... with either or both of the main protagonists in danger. They were the hunted.
One of it's main influences was Kolchack The Night Stalker and that was both... with Kolchak being a barely capable monster hunter who often ran away in fear before managing to (sometimes inadvertently) win out over the creature.
Supernatural... certainly a 'monster hunter' show... but also horror in the early seasons. Later the bros became seemingly invulnerable.
Call of Cthulhu is a 'monster hunter' game as well... but also solidly horror.